About 12 years ago, I did an exhaustive search for a good mixer. I looked at different Kitchen Aids.
Just by accident, one of the sales people at one of several different "professional/commercial" supply places that I was visiting, mentioned that there is a difference between high end Kitchen Aid mixers.
He pointed out that the "true" commercial Kitchen Aid has an overload "reset" switch, and has metal gears in it.
All the others have paper gears and no reset switch. If one of those overloads, the paper gear strips and then you have to take it in for repair.
The motor in this commercial KA mixer was only slightly more powerful than the others. I'm thinking I remember it was 350 watts vs. 325 watts for the others.
It has an accessory port on it like the non-commercial KA varieties, and while the food grinder, and other attachments state they are not for commercial use, they fit just fine in mine.
I also noticed that the stainless steel bowls did not have curled lips on them like the "residential" KA mixers. That was for making sure they would clean properly in a restaurant situation.
The blades were also made of metal, rather than plastic like the non-commercial KA mixers.
After over 12 years of use, the motor needed resetting only once, and I've never had a problem with anything else about it. For saying that, where's some wood to knock on? :)
I did replace the food grinder attachment kit once as the feed chute where the the "axle" is started to crack a little.