Hobart is the cheaper version of Miller. I have both (Handler 210 and MillerMatic 211). They are supposed to be almost identical, and size and case/housing-wise they are. But the Miller's wire feeder is more consistent, and I like how it's set up better as far as changing the spool. Just easier to use than the Hobart is. The 211 also welds considerably hotter; I do not know what the deal is but you can hear/see/feel the difference when both are turned up to the highest settings. Also in my arsenal is a Lincoln 140 which is 110v only. The Hobart and Miller are MVP (multi-voltage plug) so if you were in an area that only has 110v service (20A!) it is still able to be used; but if you have 220v, USE IT. It welds MUCH better and the feeder works better. As far as the Lincoln, it was a unit that I purchased at a garage sale for pennies, and I rarely use it, and when I do it's just because I feel sorry for it sitting in the back corner of the shop all by it's lonesome. Between the Hobart and the Miller, I use the Miller a LOT more. Actually I'm probably going to sell my Hobart to my brother if/when he comes up with the money.
One thing worth mentioning is autoset. Miller's Autoset works pretty good! I was skeptical of it when I bought the unit and figured it was simply a gimmick, but I'm here to tell you, if you have .030 wire in it (which runs sweet) and set on the autoset feature, it will automatically adjust the wire speed based on conditions and voltage. I've noticed that it "auto-sets" even if I'm welding along and hit a patch of dirty metal, it will adjust the speed as it sees fit, works wonderfully. Must be used with 75% Argon and 25% CO2, however. Straight CO2 is what I learned with and autoset does NOT work with it (at all).
I had the Hobart already and at the time wasn't really shopping for another welder, BUT the Miller came up on sale brand new for exactly the same price as the Hobart plus it came with a free spool gun. Figured I'd use it for some aluminum fab work that didn't require a TIG, but never really used it much. The thought was, buy the Miller, then sell the Hobart. And again that is the plan--assuming my brother will come get it soon. If not, I'm putting it on the market.
The dual voltage really doesn't have a sacrifice by itself, however, using it on 110v limits your work. You're not goign to be able to put full voltage (heat) into welding, so if it's about 1/8" steel or less, you're fine with 110v. It feeds ok, but on 220 it works a little better. All it is, is an adapter that allows you to plug it into either 110 or 220, and internally it senses and works without you doing anything else. I've used mine on both and almost always use 220 as long as I'm not carrying the welder somewhere where 220 isn't available.