I'd say these machines fit into the "240 volt more-serious-hobbyist" range:
Lincoln:
"Easymig 180"(plastic drive - cheaper)/"180 HD"(plastic drive - cheaper)
"PowerMig 180t"(metal drive - better, more exensive)
"PowerMig 180c" (metal drive & continuous voltage control - more expensive)
Miller 180
Hobart 190 or 210
I'm in the market for one of these myself, so I've been doing lots of research lately.
You have to be careful with the Lincolns, the ones sold in home depot, etc. have plastic drive rolls. This is inferior to metal drive rolls. If you use it a lot (which anyone who's going to drop a few hundred dollars on something probably will) the metal ones will last longer and give more consistent wire feeding. Lincoln 180s with plastic drive rolls and 5-tap power adjustments can be had for $650 on sale here, regular $800ish. More like $900 if you want metal drive rolls. Even more if you want continuously variable power output (like a volume knob instead of 5 selector notches - some sheet-metal guys REALLY like that feature. I don't find it a big deal.)
I've heard from first hand users that the Hobart 190 has noticeably more power for welding 1/4" steel than the Lincoln. 1/4" seems to be a stretch for the Lincoln 180, whereas the Hobart seems to be able to do it without trouble. Also, the Hobart 190 can be had for $700ish at tractor supply, and has 7 power settings instead of 5 like the cheaper Lincoln. It seems to be the way to go for me, I think I'll be planning a trip to Grand Forks Tractor Supply to pick one up later this year.
The Miller has a few features that would be nice if you were going to use the welder all day every day (as I'm sure some of you professional welders must do) but for me, they do not even come close to justifying the cost difference from the Hobart, which can do everything the Miller can - just a little slower or not quite as pretty (kinda like myself
).
Good luck!