[QUOTE=Rambo_The_Dog]For welding sheet metal - I do prefer the 110v, the 220v even on the lowest setting is a little more difficult to weld sheet metal with in comparision.
For maximum versatility though a 220v gives you more options for welding heavier stock.
As mike mentioned the welding method makes a difference and you can also use a copper sheet directly behind the weld to help burn thru issues and heat dissapation and there are also compounds that help prevent warpage like this stuff I got from Eastwood.
[That Eastwood stuff sorta reminds me of the old days when we used wet rags to keep the heat down and prevent warpage when brazing a piece of sheet metal. Thank God for MIG welders for this job, it sure makes a difficult job a lot easier. Oh BTW, we finished by using lead and not bondo and some of the stuff we did then is still around.