Well, Ady tried to do Empire in 1080p, and I remember several 1080p clips that, quite frankly, looked ridiculous because the source for stuff Ady was adding to the shot was far too low a resolution to look good at 1080p, but it was all he could use. That's why he decided to do the Revisited saga at 720p instead.
I think. My memory could be failing me on this one.