Being a Welder myself i know for a fact that:
A. You CAN weld Aluminium with TIG, MIG and ARC (I've done all but Ali-Arc).
B. Most people find MIG a lot easier than TIG but once you get the hang of it TIG you can produce some really nice and srong welds.
C.But personally for welding Ali i find TIG a lot easier as Ali-MIG welds get contaminated(go black and crappy and just wont fuse the two pieces of ali) very easily if the Ali is not cleaned well.
D. No one method is necissarily Stronger than the other it all depends on the heat going into the weld, the amount of filler added, the size of the weld, etc. etc.