[RMS]

I started out with stick welding, I have 5 welders now. I love my Miller tig welder/stick welder. You could do that Chassis stuff with 7018 3/32 wire its awsome stuff! Get a used - mid sized tig welder most will be able to stick weld too. If you can't see this as an option then I would say go with MIG, I like Miller myself but also like Lincoln, and Hobart.

STAY AWAY FROM THE OLDER USED LINDY MIGS.

Now if you are going to use mig for critical rollbar aplications make sure to talk with the supplyer of the consumables to get the right wire and gas/mixture for the steel/alloy tubbing you are welding.

One bad thing about critical MIG welding is that it can be finiky/tempermental if joints are not preped properly, a weld can look good on the surface but have perosity/holes on the inside one crash with this type of weld and it will snap right off. 7018 3/32 Stick is more forgiving NOW at the same time if MIG is done right it will be fine.