I had ordered an SP175+, only to go pick it up and it was not the Plus model. The guy made me a deal on a Millermatic 175, it has the infinite adjustable controls as well. I am very pleased with it. Using the .024 wire that came with it, you can weld a tin can if you're careful. I just stepped up to the .030 wire for some 14ga.- 1/8" materials I'm using for my welding table. You have to be a little more careful with the thin materials as you go up in wire size, but it's just getting used to what settings to use in the different situations. The wire is very easy to change (contrary to what I believed) so I'll keep the .024 around if I ever need to go that thin.
I guess to answer your question, I like the ability to adjust things slightly if I'm burning through.....verses having to "click" to the next preset level. You can get the Miller for roughly the same price as the regular SP175 AND get the infinite controls.