Anyway, abge, I have no experience with T-Mobile, but I do use AT&T, like you. I'm surprised you dislike their coverage. True, it completely sucks in rural mountainous areas. But overall, I've found it to be pretty good nationwide. (Of course, I don't have a smart phone, so I can't comment on data, which is perhaps the difference).
I say this not to contradict you, but to point out that, if your'e moving (I don't know if your new job is in the same place), you may like AT&T better where you're headed.