verizon will most likely be your best choice. I just went through this process. It really depends on where you live and where you want to use your phone. Verizon seems to have the best coverage in the Raleigh area. I would not recommend T-Mobile, their coverage is very spotty. Remy Hesketis a cell phone expert. Maybe she will chime in here as well. Terri
I have Verizon and haven't had a single problem. My job takes me across the entire state and all along the east coast. Coverage has been excellent. In the past I've had several clients who've had to fight with Sprint over billing issues and trying to end a contract, once it's expired.
In my previous life, I was in the field and sold all 4 major carriers (Best Buy Mobile). Here's the deal:
1) If you're a traveler (nationwide) go with Verizon. They've got the best coverage overall. There are some spots that others are better (S. Cali is AT&T territory, while Rocky Mount is Sprint territory). Coverage Maps lie, no matter who you go with, so call the Best Buy Mobile manager in that area and they can tell you who actually works well in areas you frequent. They are the most expensive, but you pay for coverage, which is what you get.
2) If you're an international traveler go with AT&T for now. It may change in the next few years b/c of LTE, but that's a different topic. Rates are ever so slightly cheaper than Verizon, but not that much. Coverage can be spotty in the mountains in NC and despite previous ads, they do drop a lot of calls.
3) Sprint is the cheapest if you want unlimited EVERYTHING (text, data, voice). Coverage is ok, though customer service is a hit or miss, it is as predictable as the weather. They're internal billing gets changed a lot, so you can see huge issues with your bill if someone didn't put in the right code at one point in history. There are some data/voice issues (such as voicemail) that have peaked recently, I'm assuming they were upgrading/repairing thier system.
4) I like T-mobile the best because of customer service, pricing, phones are ok, but their coverage is not as extensive as I need. They were Suncom here in NC and it will get better when AT&T eats them up, but then you have AT&T issues. There are areas of Chapel Hill where they somehow got approval from Chapel Hill to put in a tower when no one else could, so it's actually one of the strongest carriers in Chapel Hill. However, if you travel a lot, especially in more rural parts of the country, you can be left hanging.
I know this is a little late, but I hope this helps :)