I’m partial to AT&T because it’s my provider (although they didn’t help at all when I was in Europe; my phone never even realized where it was or updated the time), but it probably would be advantageous to be on the same carrier, maybe even with some kind of family plan type thing. There’s also the whole concept of “My Five,” in which you can call/text five people an unlimited amount… I would go to the stores of the providers (or call) and ask what the best plans are for your situation, get quotes, then compare.