I've found that it makes a lot of sense for me to just finger barre chords instead of power chords and then just strum the lower notes to play the power chord (really just an incomplete barre chord). It seems to make a lot of sense to have my fingers fretting a proper E or A based barre chord rather than a power chord since you can play a power chord off of this fretting but you can't play a full chord off of a power chord. It seems like a bad habit to ever fret your power chords with only three fingers when you can just fret barre chords at all times. Better strengthening for your fret hand, and you'll always be in position to play full barre chord when you need it. Is there a drawback to this method?
I only use power chords when using distortion. playing anything more then three strings with distortion sounds like crap. But then again, I know my theory so I'm capable taking a six string bar chord and making work for three strings and have it including it's important notes. Like I could take an Am7 chord and just play the root third and seventh, making a three note chord bu including the noted that still make the chord an Am7.
if you fret the whole chord and your playng with distortion, then moving your fingers around might make a horrible scratching noise.