OP,
If you want to kick it up a knotch, I would say definitely go for the 220 volt machine
IF you think you will always have a 220VAC outlet where you will need it. It totally blows when you don't have power and can't use your machine.
Even with the 110VAC units, you can weld anything you would do at home, it just comes down to technique.
As Racer47 stated, you can resell it. In fact, i searched a little on OfferUp. For example, the first machine shop I worked in had a Lincoln SP100. The owner bought that for ~$600 and people are still asking about that. That was a great machine for the price. I burned on it for >8hrs per day for over two years and it still worked great ten years later.
If I was going to do just car stuff, I would seriously consider a TIG. Anything you make will be way more bitchen with an
ARC welder for sale. The Miller EconoTIG that Midlife Crisis has is another good (old) machine. If you do step up to a TIG, make sure that you get one with AC capability, so you can weld aluminum. You can always add a wire feed to a TIG.
Stick welding has no place on a car!
Flux core is tractor mechanic $#!+.