To make things simple, the iPhone 5 is being released on all 4 major networks: AT&T, Verizon, T-Mobile, Sprint. Fortunately, you only have to worry about AT&T and Verizon (there are 7 people on T-Mobile and only the Sprint CEO uses Sprint. I said it.).
To make things even simpler, if call quality/reliability is of utmost importance, go Verizon. If data speed (uploading and downloading) and using data while on the phone is more important, go AT&T.
That’s it. If you must know, Sprint is somewhat similar to Verizon and T-Mobile is near identical to AT&T
This may be the greatest video ever describing AT&T vs. Verizon for numerous reasons. Point of the story: 5 dropped calls for AT&T and not a SINGLE DROPPED CALL for Verizon. Boom.