I like the pinky for E5 chords. It allows for a great walk down the major scale on the D and A strings using your index, middle, and ring fingers. You can do this while still playing the E power chord. Very good way to add intrest to the chord.

I also like the pinky power format on the E5, because it is easy for me when I change to an A 5 chord. My pinky is ready, right where it belongs ,