I have an iPhone 5 and my wife has an S III. The standby time seems considerably better on my iPhone 5 unless we’re in an LTE zone, and then my iPhone 5 drains much faster than her S III. I’m guessing this is due to relatively similar power draw of the LTE chips, but a much smaller battery to draw from on the iPhone 5. Other components matter less because they are proportional (i.e. smaller screen, smaller battery). I had (and loved) a Nexus 4 but I found the battery life to be considerably worse than either of these phones, and I had a RAZR Maxx HD and found it to be much better. The S III and the iPhone 5 feel really similar in battery life in my experience, each better in certain categories but averaging out to about the same. I think you’ll be very happy.