It sometimes depends on the networks used and the phones. With the case of T-Mobile the prepaid and the regular service are both using the same technology and towers so you should see the same coverage. The only difference would be the ability of the phone to connect to those towers, which usually isn't a problem these days, but it's possible you would see a difference.

All,
What exactly is the difference in signal coverage between a prepaid plan and a contract plan? I have heard opinions ranging from not noticeable to extreme, I'm hoping someone here has used both and can talk from experience.
Thanks