I had a 3g and now have a 5. The different is night and day. speedtest app on the 5 is pulling 27Mbps down and 7.38 up. Its faster on my wifi at home but I don't wait on anything. If your going to compare, go to an AT&T store and handle both. I love the weight and size of the 5 and the battery life is much better than my old 3g. 

AT&T's site shows the standby times to be in favor of the iphone 5 by 23 hours, talk time to be about the same 8 hours.