The extra heat in gas welding also distorts, gas welding a lump of steel is totally different to welding thin sheet steel with a shape to it. ALL the professionals I know (some with more than 40 years exp.) would not choose gas over Mig. Gas does have a place in a bodyshop, but it's use is very limited these days IME.
I would say that if the OP can gas weld then the progression to mig will not be a steep one, or shouldn't be.