[quote name='JJSP']You do know the iPhone 5 benchmarks higher than the SG3 and costs the same, right?[/QUOTE]
That's not quite true. There are conflicting reports on the performance of both phones using the same benchmarking app. If anything, I'd put them at close to a dead heat since their scores are usually very close.
I upgraded to an iPhone 4S from a Droid Charge cause I missed the apps. Then when the SIII came out, I switched back. Main reason being the unlimited grandfathering on Verizon was ending and if I didn't upgrade then, I'd be forced into the shared plans on Verizon. For the most part, I don't miss the iPhone too much. I admit the SIII can be buggy sometimes. There are a few occasions where apps would freeze up and crash.
But on the whole, I don't really miss my iPhone that much. I get lost quite easily and rely quite a bit on the Google Maps. Turn by turn voice directions is a godsend in those situations when I'm driving somewhere far and unknown. Apart from that, the cameras are on par. The camera on the iPhone 4S I'd rate a little better performance-wise but the SIII has way more photo editing and camera options, if that's your thing. I haven't tried Apple's map app yet, but so far I've heard generally ok things about it.
I think ease of use leans towards iOS because of its simplicity (not a knock, but it is streamlined and controlled to make it easy for any user). But if you like a little more control and integration among your social media stuff and email and whatnot, Android still has it beat.
Ultimately, it comes down to a matter of usability. Like others have said, identify your main uses of the phone and move on from there. They're both very good phones, it just comes down to what you're happy with.
Also, does Sprint have a similar 30 day return policy on phones? I know Verizon has that 30 day return policy where you can return the phone if you're unhappy with it. Another thing you could do is maybe order one and give it a test run then go with the other. That way you have a little time to figure out if you're completely happy with either. A little bit of a hassle, but this way you get real hands on time with it.