I am a pro tech and use SO, Stahlwille, SK, Wright, Mac, at work. I have Cornell and gearwrench at home too.
SK- nice chrome, feels good in your hand, but the open ends spread out on the smaller sizes. Same thing with their flare but wrenches. This all applies to the pre-china Cman pro line wrenches too, since sk made them.
Wright- I only have two large sizes of them and they seem fine for the price.
Mac- I've always tried to give Mac some love but they often disappoint me. I have the Mac edge ratcheting wrenches which they no longer make . Warranties the 12mm and ended up with a facom made (which IS better) version that ratchets in the opposite direction as the rest of the set, and doesn't fit the tray. I also bought a long knuckle saver 13mm thinking it would crack bmw tie rods Loose for alignments, but found that the open end just slips around the fastener worse than a standard combo wrench. Mac truck dude said "they're made like that to slowly round off the fastener and not slip around the fastener quickly and bust your hand" (???)
Stahlwille- I have the open/box 15 style set and they have a deep box end wich I use a lot to get hard to reach stuff. Nice tools but the chrome does tend to peel over time. The open ends aren't that strong either.
Cornwell- nice tools, good chrome on the wrenches. Weird how the open end offset faces the other way compared to other brands. V groove style which fits the fasteners better, but in theory isn't as strong as an arch
Matco- I only have a few random Matco wrenches and they seem fine. I'm pretty sure they aren't expensive
Snapon- I waited a long time to get my hands on a flank drive plus wrench set. They were too much money for my taste, but I ended up buying a normal set from the 70s/80s and using them for a while. Then a BOGO deal came up for the flank drive plus set and it came with a free SAE set. I don't work on sae stuff so I traded my 100.00 eBay wrenches in on the new flank drives and sold the sae set on eBay. Pretty much broke even and now I have what I consider the best Serb of wrenches you can get. The weight is perfect, the shape is good and doesn't hurt, the chrome is great, and the open ends will turn things that alll of my other wrenches slip on.
It's not voodoo. Snap on is good stuff. You just have to decide whether it's worth it for you to need them. Many of the same jobs can be done with any other brand.. but there are times when the so stuff shines