Pipe welding on a thin wall motorcycle frame is like tilling a flowerbed with a D-9 Dozier and MIG welding is like painting your motorcycle with a weed sprayer. TIG is the strongest and the most attractive. TIG welding is the artistic class of welding on motorcycle frames. I shouldn`t be so hard on MIG, but it is mostly for production lines and after many times it does get better welds and is faster. I would not even consider a stick weld on a frame unless there was nothing else.
When done with TIG...you`re done...no messy flux nor nodules to clean up. Heat is a factor also because frames are alloys that need a minimum temperature weld so not to crystallize the metal around the weld bead. Go TIG only on bikes,but train for all types of welding because they all have their place and I would hate to have to weld a pipeline with TIG.