I like power chords ´cause they are simple and you can do a lot with ´em especially combinig them with riffs a la Metallica. But clean power chords are like open chords with distortion unmuted. There´s no power at all.

One cool thing wich I learned from Petruccis video is to mix dist power chords with open clean chords. To preform this live, you got to be 2 guitar players but it´s cool when working in studio. You can get some really cool chord and a little bit unusual/orginal chord progressions with this technique.