I build frames and own a bunch of welders arc,TIG,MIG. My preference for most of the work is the 110V MIG the 220 gives the same results (heat penetration) I just like my small welder. I would not arc weld anything on a street rod frame, I do when I do trailer frames but that is a lot different in metal and final cosmetics. I TIG motor mounts and cross members but that is more of what I do rather than necessity. MIG 110 or 220 will work exactly the same although I know a lot of the 220 units come with a lot of options for presets for novice welders more so than I see on the 110. Also gas versus gas less is the cosmetics for a gas weld is far superior to flux core. The only other argument on a 220 over a 110 is that a 220 can be used on thicker metals by turning up the heat but this would not be needed in building a frame for a car.
Cunningham and Hersh Hot Rods