Originally Posted by JE78
I guess i'm speaking for my 2 friends who have the S3 and are always charging them and then ask me to trade phones with them
. I'm also coming from a Galaxy Nexus with a 2100 battery and I couldn't make it though a day with, I always had to put it on the charger when I got home at 5pm because my battery was under 20%, this was with the phone setup for conversation and very minimal use.
I don't know how your friend's GS3 are used but I never saw my friend's GS3 being always charged. All of them are saying it's easy to go over a full day and some more with GS3. Just because it has the same 2100mAh as Galaxy Nexus doesn't mean that battery life would be similar. The processor/radio chipset in GS3 is 28nm Qualcomm Krait, which is far more efficient than 45nm OMAP4, CMC221 LTE in Gnex. GS3 easily outlasts Gnex by long shot due to more efficient chipset.
Maxx HD has the same chipset as GS3 and almost identical HD SAMOLED screen. So between GS3 and Maxx HD, battery life difference will be simply matter of size difference. Also there are extended battery with capacity greater than 4000mAh for GS3.