I believe a lot has to do with the chip manufacture. From what I understand, the newer chips like the ones in the GSIII and Note II is manufactured using the newer 28 nm process while the older chips like in the Bionic and the Rezound were manufactured using the older process (30-something nm?). Supposedly the new chips have a much lower power consumption. The SIII has a 1650 mAH standard battery and my son can last the entire day on that, and while he doesn't use it when he is in school, when he is out he regularly streams Pandora.