Default Starting Over

I currently have a rooted HTC Evo 4G LTE with Sprint, the contract is over and Sprint no longer wants to offer unlimited data. So it is time for me to find a new provider, a new phone.

Which provider has the best 4G LTE signal, which would be the best phone.
My requirements are that the phone be able to be rooted, and that I have control of the bootloader.
As far as I know HTC is the only bootloader that you can have control.

I think I want to go with T-Mobile, since they have a sensible unlimited plan...which would be the best phone for this project.
Phone: HTC Evo 4G LTE Rooted S-off
System: Intel I7 Extreme 24GM RAM 12TB NAS
Tablet: Windpad 110W Dualboot Windows 8/Android 4.0.3
Laptop: Ubuntu 12.04 Linux