Model for model, there is NOT a difference in units depending on where you buy it. The so-called "pro" series are theoretically only available from Plumbing Contractors and Distributors, but these days that is a bit of a myth.
The pro-series models probably have more pieces made of SS. Other then that, hp is how they differ. They seem to claim increasingly quiet as price go up. I have a basic compact. Had it for a few years now. It is plenty beefy enough for what we do, and I would not pay more to get a disposer quieter than this. We like it a lot. NOW, if you like to put whole chickens in your disposer, get a one horse!!!!!!