According to Sprint's website, the winner is the 16GB iPhone 5 with shipping times posting two weeks out while the 32GB and 64GB show delivery dates of September 21st. The other two US carriers, Verizon and AT&T show dates of 9/26 and 2-3 weeks ago respectively. Maybe Verizon has a larger allotment of iPhone
Of course, if you do chose Sprint, you won't be able to make calls and surf the web simultaneously so chose accordingly. If you're like me and live in San Diego, I don't even see a roll-out date for Sprint LTE so until then, I'll be sticking with AT&T.