Speaking as an ex-mechanic with a tool box full of Mac and Snap-On tools I can say that I have no idea why any home mechanic would need anything more than craftman or husky tools. Frankly, in my opinion, most mechanics use them for the aforementioned reasons of convenience and easy payment options. Not to mention that some techs get a sense of pride by having $20K worth of snap-on tools in their box.
The finish on them is nicer than what is on cheaper tools. No question about that. All of my wrenches started off with a lovely mirror finish but that faded over time with use so I dunno why that's really a selling point.
I bought most of mine while I was in tech school when Snap-on and Mac gave us 50% off of anything we wanted to order. If not for that, my box would have been filled with craftman tools.