I have been involved in sheet metal fabrication
and welding my whole adult life (18 yrs) and
would agree with the other "pro-tig" opinions.
It is a much smaller precision weld that requires much less filler rod/wire than mig.
Warping can be easily controlled/corrected by skipping around and immediately hammer and dollying the area. Pretty much the same technique used in gas (oxy/acy) welding, which some old timers will say is superior to tig.
(which I would agree with)
Tight fit-up is critical...butt joints only, no laps. Excessive grinding on mig welds can also
cause work hardening or brittleness of the metal. Not to say you can't do a respectable job with mig, it's just that tig (or oxy) are superior and it is possible to have seams that need very little or no body filler. That's why the big boys use it.
