Reading this Marco Arment post, I wonder if I should have gotten Emily the 64GB model. I didn't think about what it meant to capture HD video. More than a phone discussion though, it's a carrier comparison. There's a lot I didn't know (emphases mine) ...
... Under ideal conditions, AT&T has the best data speeds and Verizon has the best voice quality, but almost nowhere actually provides ideal conditions, so it really depends on which carrier sucks the least in your area.
All three carriers’ plans are priced in the same ballpark.
People often say that Verizon covers fringe areas better, but in my experience, AT&T is comparable — sometimes one works and the other doesn’t, but neither more often than the other.
I don’t have much experience with Sprint, but the little I’ve had suggests that it doesn’t quite provide the coverage and strength that Verizon and AT&T do. Sprint phones can roam on Verizon’s network if there’s absolutely no Sprint signal, but in practice, that doesn’t happen often, and the phones will prefer a weak Sprint signal to a strong Verizon signal.
Sprint is the only carrier offering “unlimited” data.
Verizon messes with your data uncomfortably — they recompress JPEGs to save bandwidth, and they watch the sites you visit to collect (and presumably sell) the aggregate stats.
... any iPhone 4S you buy in the U.S. with a contract at a subsidized price (less than $649) is still carrier-locked. You can’t change carriers later...
The carrier lock really sucks. Even after you've paid your $800 or so for your $650 phone, it's still carrier locked. Of course it's two years old by then, but Emiiy's 2 yo 3GS still works real fine. Yet another reason that American geeks hate mobile phone companies.
If you're trying to find out which carriers work in your area, my friend Robert M recommends Antenna Search as a guide to your local towers. I discovered my home is in an area with relatively few antennae -- except for 3 immediately nearby. We don't have coverage problems.