I can't even believe these arguments keep flying (and starting anew). For the budget minded, there are a number of choices that are not the big 4 companies. Many of these use the same network as the big 4 but offer prices at about 40%-60% of the costs. If you are budget-minded, the dominant issue is cost: cost of the phone plus cost of service over time. OP seems intrigued by the Tmobile option for cost of service.
Many of you are answering a question of which network is better (irregardless of cost). OP didn't say that money was no object; he's looking for a better deal.
OP, the one good bit of advice you've got so far is to be sure the network is solid in the area where you are moving. Once you identify the best network, look for a way to use it without paying the maximum toll. If it turns out that AT&T is the best network, consider StraightTalk or Net10 running on the AT&T network. It gets you all the benefits pitched by these "money is no object" guys on the "best" network for the area at about half the cost of AT&T.
For example, we just went with iPhone 5 and Net10 running on AT&T. We get every AT&T benefit except visual voice mail (which is no big loss to us). Cost for "unlimited*" talk, text, data: $45 per month. Net10 defines "unlimited" data on AT&T with a hard cap of 1.5GB per month but that's no problem given we are almost always around wifi. A second line can be added with unlimited everything for $40 more per month. That's $85/month for unlimited everything on 2 lines.
Like Tmobile, you have to buy the phone out of pocket. If that's too dear, Straight Talk through Walmart has the same no-interest purchase plan on an AT&T credit card. Straight Talk is the same company as Net10.
If it turns out that Tmobile is the better network in the area, Net10 has their service on Tmobile too. If OP already has an iPhone(s) they can use, then $45/month is way better than any of the big 4's plans. Since it's on the same networks, there is no major advantage for paying about twice (or more) for them. You need to really love visual voice mail to justify 2X or more in the monthly fee.
OP, if you don't actually need unlimited everything, limited plans can be cheaper. Tmobile has a $30/month plan with some limitations. Consider your real usage to decide if you actually need unlimited everything.
And OP, if you can stand to let go of iPhone, look up Republic Wireless. They can set you up with an Android smart phone with "unlimited*" service for as little as $20/month. They lean on the Sprint network so be sure it is solid in the area. Their (good) approach is to configure the phone so that you are using wifi when wifi is available and cellular only when there is no wifi. As such, they can offer much cheaper plans. Even if Sprint is only so-so in the area, if you are around free wifi most of your day, they might be a good option.