Mig is great for thin stuff. All the panel beaters use it due to it not heating up the surrounding areas too much i.e so it won't affect the paint on panels or heat distort.
ALso Mig is very quick in comparison to any of the other techniques.
If you get one get one that has the capability of doing gas and gasless. If you get a second hand one check it out well before hand. I bough one and I had to put a new liner in it and a few things which was a bit of stufffing around but it's good now.