I may just lean toward miller since it was the first decent welder I ever used. I've never had any problems w/ the little MIGs or the synchrowaves BUT every machine I've had or used was probably less than 10 years old. When comparing used vs. new the warranty is always a big factor. Now that I think about it ALL the ancient, massive, scratch-start TIGs I've used were Licolns. Built to last. Back when it was HELIARC welding.
FR, Also had a Hobart MIG (135?) that was a real workhorse.
Wait... aren't all these companies owned by the same monster corporation now anyway? Kinda ruins the whole 'brand loyalty' thing. Same machine in each color. So, FR you prefer blue, red or tan? Oh, and ESAB yellow.
(ESAB makes a sweet little MIG/TIG/STICK one peice unit....)
cyberweld.com is going to have the best price, next day free delivery? They sell the tanks too. C20-25 is a good all around gas. Price wise you should be good to go for under $600- gas included. The little 125's go for $300-ish or They have the Hobart 180 on sale!!!! $449 is 1/2 price! Either way it opens up a whole world of fabrication possibilities...You won't regret it for a minute.
So, there you go. Get a little 115v gasser, better welds, more versitile, plugs in anywhere. Gasless, in my opinion, is really only for outdoor apps where your sheilding gas would be unreliable.