When I bought the recent Costco model, I was intrigued to find out what was hiding behind the Costco brand Kitchenaid model. Interestingly enough, it turns out to be a Williams-Sonoma 610 model. This got me asking what is the difference to the 600 model, and why does a 610 model even exist? After taking my Costco model apart, doing a significant amount of research, and acquiring the 7 qt model and investigating it, I came to the following conclusion:All models, the 600, 610, 620, 6000, 6500, 7qt residential, 7 qt commercial, and 8 qt are essentially all the same models. They have the exact same form factor and with the exception of the 6000, fit the same beaters and bowls. They differ mainly in motor, transmission, bowl, and beater (that needs to match bowl size). And some models have plastic knobs whereas other have metal ones.600: This is the base model. A few years ago Kitchenaid changed the transmission case, that holds some sprockets in place, to plastic. This was changed back to the old metal cast case from the 6 Series now. It has a 575W AC motor.610: Is the same as the 600 with the same transmission, but a different 590W AC motor. I doubt that the extra 15W this motor is rated for makes a difference. The 600 model collected a lot of critic from people doing heavy doughs. My assumption is that Williams-Sonoma requested a more robust motor, perhaps with higher torque. The control electronic is a very simple triac motor control. It looks similar to the 600 control, but has the hall speed sensor soldered on. It also misses the IC from early 600 models. The wire whip is not the one from the 600, but the one from the 7 and 8 qt models. The Costco model has metal flat and hook beaters instead of the coated ones.620: Is a 610 in fancy colors.6000 HD: It has an entirely different transmission and motor than the 600, 610, or 620. My assumption is that the transmission is the same as in the 6500, 7qt and 8 qt models. The motor may or may not be the same. The 6000, like the 6500, is rated as 1 HP. It could be the same motor from the 7 qt and 8 qt and might be electronically limited or simply derated on paper. The bowl, and therefore the beaters, are totally different than on the 600 models. The bowl is taller and narrower. Because the pins that hold the bowl are narrower, you can only fit 6000 bowls, but not those from the 600, 6500, or 7 qt, 8 qt models. This is by the way also the old Costco model.6500: Appears to be a 7 qt model, derated for 1 HP with a fancy 6 qt bowl. The cover of the planetary gear facing the bowl looks more robust.7 qt: Its motor is rated for 1.3 HP. The 7 qt appears to fit all the bowl from the 600, I actually tried this out, even with 7 qt beaters. In reverse, the 600 fits bowl and beater of the 7 qt.8 qt: In all likelihood a 7 qt model with a bigger bowl and a finger guard. Motor is rated the same. It should fit all 7 qt and 600 model bowls.The 7 qt and 8 qt also exist as commercial versions with an orange power cord and a commercial use warranty. Otherwise, my assumption is that they are the same as the residential models.Confused, yet? What should you pick?In my opinion the biggest differentiator is the AC vs DC motor, not because the motor is AC or DC, but because of torque, transmission, and speed control design. The DC motor of the 6000, 6500, 7 qt, and 8 qt models is significantly beefier than the one of the 600 Series. The DC motor uses a digital PWM speed control that holds speed exactly and increases torque as needed. The 6000 and 6500 may or may not have the same motor as the 7 qt and 8 qt models, but are rated with 25% less power. As I said, this might be paper derated or electronically limited, or actually it has a slightly smaller motor. The DC models also are significantly quieter than the transmission and motor combo of the 600.The 600, 610, and 620 use a very primitive triac control. The 610 and 620 have a slightly more robust motors but use the same transmission as the 600. The triac control will not increase torque as well while holding speed, which specifically will be noticeable with heavy doughs. These models are very noisy. Because of their simpler design, the 600 Series is cheaper to repair than the DC models. Sprockets are a couple of bugs and even the speed control is inexpensive.The 6000 HD appears to be the oddball when it comes to bowls. It uses narrow bowls that need their own narrower beaters.All other models use the same bowls. Now, it might make little sense to put an 8 qt bowl into a 600 where the motor is not strong enough. The dough hook might be the same, but you need more force. The wire whip has more wires on the 610 and up models. I do not see why it should not work on the 600. The real difference is in the flat beater. While you mostly can use the larger (flat) beaters with smaller bowls, like use a 7 qt beater with a 6 qt bowl, if you use a 6 qt beater with a 7 qt bowl, you just do not reach the top of the bowl. The 3 qt bowl should fit all models, even the 6000 model, because it has holes for the narrower pins, and comes with its own beater.The dough hook exist in stainless, aluminum and coated aluminum. The flat beater exist as stainless, aluminum, coated aluminum, or with a silicon lip that saves you from interrupting and scraping the bowl walls. The wire whip is always stainless. Only stainless and coated aluminum can be washed in the dish washer. Some people complain about the coating flaking over time. While various packets exist that bundle coated or none coated versions, only the commercial 7 qt and 8 qt version contain stainless beaters. Beaters are quiet pricey but can purchased after market, even from third parties.Depending on the sale you are getting, the price difference between the models might not be actually that much. I would not get a 6000 because of the weird bowl shape that locks you in. I found the price difference between the 7 qt and 600 models to be about $100 with the right deal, the 6500 actually could be more expensive. The 600 comes in all kinds of colors, of this is important to you. All other models are limited in colors. I decided for the 7 qt model because I wanted to make pizza and bread doughs and simply bought 5 qt and 3 qt bowls for the smaller jobs. I would buy an 8 qt bowl if I ever needed it.I hope this information makes it easier for you to make your own decision.On the picture, left the 7 qt model, and right the Costco 610 model.When I was in grad school, back in the 1980's I worked for Hobart Corporation for a couple of summers.I sold KitchenAid Mixers and attachments, then I sold Hobart food equipment to restaurants in the SF Bay Area.I sold mixers, slicers, scales, food cutters, and microwave ovens. Hobart was the most expensive, and the absolute best equipment and probably still is. I would try to sell a Hobart Microwave or mixer, or Speed Drive, and the potential customer would complain loudly about the price, and tell me to go away. So, I would offer to allow them to put the piece of equipment into their operation for free, for a month or so, just as a goodwill gesture. No obligation. I would come back a month later and come into their restaurant, and start to unplug the device to take it away--and be stopped every time by the customer. We would do a contract for the original price, and I would always make the sale.With Kitchenaid, it was so easy to sell the mixer. It was more powerful than any other stand mixer on the market by far, and the 5 quart model was similar to the N-50 restaurant model. The only difference was the restaurant model had a significantly heftier motor and gearbox, and was all anodized aluminum. It sold (at that time) for over $1,500 new. The KA sold for about $175 as I recall. Right after I left Hobart to go into software engineering, the sold the Kitchenaid line to Whirlpool.So now, almost 40 years later, I find myself in need of a mixer. I don't know much about Whirlpool, but I decided to go ahead and get my first Kitchenaid mixer (actually my mom had one when I was growing up in the 1960's).Before I did, however, I checked out the online reviews. Lot's of crazy stuff. Of course we all know that the other companies whose names I won't mention, send out trolls to purchase and then give bad reviews to KitchenAid products. The same thing happens to quality products online all the time, the other notable one being the Vitamix blender.So, some reviews about a "noisy" mixer, about it blowing gears, trouble with the 1 month return period from Amazon, etc. The reviews about it being "weak" or "noisy," with "whining and clicking" sounds were the most common.But the hundreds of positive reviews settled it for me.So I bought this mixer.And?Yup. It's noisey. For the typical person buying an appliance in this day and age, it is a fair amount noisier than some of the cheaper mixers. It's even quite a bit noisier than the old K45 and K50 that I sold and repaired when I worked at Hobart.But here's the thing:It sound pretty much exactly like the commercial N-50 mixer. Yep. The (now) $2700 5 quart commercial mixer that Hobart still sells to restaurants. Hobart sells the n-50, the D-200 (20 quart) the A-600 (60 quart), and even a 120 quart mixer to the restaurant market. If I go into a pizza restaurant and have a pizza, and I really like the pizza, i.e., it is superb such that I would return again and again for this pizza, I can go look in the kitchen, and there is the Hobart A-600 mixer sitting on the floor pumping out pizza dough.Why is it noisy? Do this. Put the ingredients for 2 loaves of 100% whole wheat bread into this Professional series 6 quart mixer. Go ahead and start it up on 2. Put the flour and salt in first. Then start adding the liquid a little bit at a time.This mixer makes noise the whole time. And doesn't slow down. Not a single bit. It kneads this bread as if it were whipping fluffy egg-whites. It doesn't matter. It doesn't sound like it's working, because it isn't.Work that would wear out any adult kneading and kneading this bread is not even causing this mixer to heat up.The sound it makes is EXACTLY what I remember the N-50 making. It has a gearbox with metal square-cut gears and one plastic worm-gear that is designed to strip and protect the rest of the gearbox if something goes wrong.There is no reset button, there is no "overload" switch, because it would trip too often and lead to warrantee returns for no reason.As far as I can tell, the main difference between this mixer and the $2700 N-50 is the color and the size of the bowl (6 qt instead of the N-50 5 quart). This new mixer has the same power as the commercial mixer--a first for the home market.Note that every *independent* review I could find indicated that the Kitchenaid was the only truly reliable mixer for kneading dough, and the fact is, if you aren't going to knead dough, you might as well use a hand mixer. The real reason for a stand mixer is for kneading dough, or a *tiny* bit of convenience.On review compared the Kitchenaid 6 quart professional to the Breville, the Cuisinart, and to a bevy of other similar mixers. None of them could knead bread dough reliably. That's right, the Cusinart and the Breville failed utterly.The Kitchenaid mixer originated from the N-50. The motor, gearbox, and of course the particular motion of the mixer were scaled down for the home market, and the K-45 and K50 were by far the most successful and well received mixers well, on the planet.It looks like Whirlpool/Kitchenaid decided to push the K-50 model up into the N-50 functionality with a more powerful motor and I think stronger gearbox, leading to this model which I have found to be far beyond what I expected in terms of counter-top non-commercial mixer.Thanks, Kitchenaid/Whirpool!When I worked in the parts department for Hobart, the joke was to call the Kitchenaid division "ChickenAid."Ha-ha. An inside joke. But I swear I will never say that again, after using my new Kitchenaid professional series 6 quart mixer. This is a serious machine. If you don't like the noise, buy your bread at the store, or build up you forearms kneading by hand.For the price, this machine was not worth the effort to even order it! I specifically ordered it so that I could make bread, which calls for 12 cups of flour. After 2 minutes of kneading, the machine stopped running! I let it cool as instructed in the book, and 30 seconds into the kneading sequence again, it stopped running. At that point, I washed everything up and packed it up for a return. Thought Kitchen Aid was supposed to be a good quality and long lasting product - not so. Then, to return it, Amazon charged me $65.03! Talk about adding insult to injury! Don't waste your time ordering one of these. The motor was not strong enough to handle making 4 loaves of bread. Very, very disappointing.I invested in the Professional Series thinking that the metal gears and other features would mean it would last for ages. It worked fine for about five years of very occasional use (I only used it a few times a year -- Christmas cookies, occasional biscuits/bread making, that sort of thing). Even though I'd purchased the model I thought was made with higher quality materials, I was always careful to not ask too much of it -- for example, I never used cold butter straight from the fridge. In spite of this, it now runs but with no "power" behind it. I can beat eggs or whip cream (maybe) but it can't "push through" even softened butter and flour. Customer service wasn't very helpful when I sent an inquiry. I now have a thirty-pound doorstop on my kitchen counter.La usamos todos los dias en el restaurante que trabajo.La usamos de forma diaria por severas horas sin problema!Es Rapida, fuerte y estable.Puedes tener cualquier tipo de masa, postre o pasta en el proceso, y no se mueve ni un cm de lugar al batir.Tiene un color muy bonito, pero recomiendo lavar con esponja amarilla suave, ya que puede dañarse el acabado brillante.Todo embona y funciona perfecto.Sin duda Hablar de batidoras Kitchen Aid, es hablar de calidad y seguridad!Esta es una batidora profesional, es potente y de gran calidad. Muy estética y lucidora. No sirve como reemplao de una Hobart de panadería pero si que sirve para hacer volúmenes un poco más contenidos.La calidad del equipo es de primera, sin problemas aquí. El motor es muy potente y tiene buen torque. La batidora es pesada y bastante sólida. Los acabados son muy buenos. Incluye 3 accesorios de metal; batidora de huevo, gancho batodor de masas y otro gancho tipo "flat beater".No se si vaya a ser muy durable, pero lo que si puedo decir es todavía existen en la familia batidoras Kitchen Aid de 20 años y siguen dando batalla.Importante: esta batidora no tiene cabeza pivotante, es decir; la cabeza es fija y no se levanta. En lugar de eso, uno tiene que quitar el bowl haciendo un par de malabares. Esto es importante porque algunas personas prefieren que la cabeza sea la que se levante y las aspas queden en el aire. Esto es para dar mayor eficiencia en los batidos.+ME GUSTA+ Color muy estético (la mía es la roja quemada)+Pesada y sólida+Excelente calidad+Motor profesional con gran torque+Accesorios de metal+Buen precio en Amazon+Variedad de velocidades+Muchos accesorios que se venden por separado-A MEJORAR- Un poco ruidosa- Cabezal no se levanta (modelos pro)Puedo decir son lugar a dudas que esta batidora es 100% recomendable.Gracias por leer mi reseña.Esta batidora es la mejor simplemente, si eres amante de la cocina y te puedes dar el lujo, ¿por qué no?, a mi esposa le encanto y pues si te ahorra tiempo para muchas cosas, ojala pudiera estar al alcance de cualquier ama de casa, pero que le vamos a hacer, solo algunas la podrán adquirir y no creo se arrepientan de esto. Por cierto es más barata que en Liverpool o Sears y si la adquieres en oferta por el prime day o algo así te ahorraras bastante.