He might mean a 4S actually.
My experience with AT&T, when I lived in the US, was good -- I tend to live and work in big cities, so I never ran into an issue with coverage (unlike, say, T-Mobile, which has definite "dead spots" around the country). Corporate-owned AT&T stores have been in my experience helpful and friendly, though until recently it was quite the challenge to get them to unlock an off-contract phone.
The 4S, the 5c and 5s are literally "good, better, best" in terms of phones. For basic use, any of them will be fine, but the higher you go the more features and better cameras and speed (of processor/graphics) you get.