Hi superfly , I had both Gas and Mig but found at the time having to rent three bottles a bit expensive and after considering the positives and negatives of both I went for Mig , I can relax a little now knowing I haven't got a possible ' Acetylene Bomb ' in the garage

also I found the Mig safer to use around cars as you don't have that Gas flame burning anything within a couple of feet of the torch

With Gas you weld , do a bit of shaping , bit more welding and so on but the gas torch is on most of the time which is wasteful whereas with Mig it's only working when you pull the trigger.
Also generally you need 2 hands with Gas but only 1 with Mig ( providing you use a head shield ) and it is so handy to be able to position panels with one hand and tack with the other , the Mig is much more ' user friendly ' but I do miss the versatility of having Gas around .