Snap On is not the only "professional" brand tools that are sold directly to mechanics from a "tool truck" - they are the most expensive according to the mechanics I know. Some mechanics say they are the best while others just say it is more convenient to buy from them because they do not have to go anywhere to buy their tools and use that reasoning to justify the higher prices.
All of the brands that direct sell from the truck cost more than the ones you can buy in the store or online.
I have used many different brands (Craftsman, Black Hawk, SK-Wayne, Husky, Kobalt, HFT, Snap On as well as others) and have mostly found that, for the most part, taken care of, they all work and last. Some are more comfortable to hold and use than others.
Currenlty, most of my hand new tools are HFT and Kobalt