The new superamoled plus on the S2 is said to be more efficient than the original, which is more efficient than LCD. The Atrix has a bigger battery. My experience is that the screen is the ultimate killer of battery life, second only to the wireless radios. I don't think the CPU has that much of an impact on battery life, especially if you are just doing boring non-gaming stuff. I really have no idea though so I'm just talking smack to waste time until a release date is confirmed.