Pros: Always seem to have better phones when I'm looking for a new one
Cons: Handcuff their phones
I do appreciate that Verizon has phone service in the metro in DC, but other than that I don't know what they could offer superior to AT&T. I've always got a fairly strong signal in the area, but I don't know who doesn't.
Phones have always seemed superior at AT&T when I've been shopping around for one, which is every 18 months or so.
Rollover minutes can't be beat... though it seems each carrier has their gimmick.
I have had less than stellar results with AT&T stores adding things I did not request to my bill when I purchased a new phone, but I had stellar results with the AT&T customer service removing said charges once I called to complain.