iPhone 5 actually does better in a few benchmark tests than the Galaxy S III due to the smaller, more efficient retina display. It doesn't have as much to render. That's... where the advantages pretty much end.
GS III has double the RAM, a bigger battery, running an OS that is leaps and bounds more powerful and customizable, has the bells and whistles like NFC with Android Beam and S-Beam, share shot, burst mode on the camera, special gesture features, and guess what? Our maps actually work properly lol