You have asked a very good question! I think it depends on the song you are playing. If as has been said, you want a garage sound, play triads predominately. You can change very quickly between the inversions ie. *top 3 strings* 232=Dmajor...ok? 432= Bminor..433=Gmajor.. 453=Eminor..all in the key of D (orG). But can you see you're only making a slight change every time- one or two fingers moving a fret or two. Imagine having to do that with barre chords...5th fret, 7th fret...3rd fret..7th fret! Besides that the sound of a power chord, is..well..powerful, maybe The Ramones yeah, but it can make yer average band sound like AM sludge....when I do it it does anyway..