Go with the 4S, ST doesn't have access to ATT's LTE, plus they aren't selling nano SIMs yet, I've heard rumors (grapevine) they'll start sometime this month, so you'll have to cut your SIM to fit in the 5
I'm going to assume that with pre-paid you don't have access to LTE. With that being the case I wouldn't pay $275 more for a 5. To me a bigger screen and faster processor isn't worth close to twice the money. I'd get the 4S and call it a day.