From a voice/data signal coverage point of view, T-Mobile is doing pretty well outdoor. For indoor, it's a different story. If your work heavily depend on solid phone network coverage (eg.. real estate agent, lawyer etc...) and you work indoor most of the time, I advise you stay with AT&T.
Otherwise, T-Mobile is much cheaper compare to AT&T. With Wifi Calling feature, T-Mobile should provide you adequate service (both voice and data).
As far as travelling & coverage, please let us know which countries you travel the most, then we can see if there are roaming support for those regions. Good luck.
Otherwise, T-Mobile is much cheaper compare to AT&T. With Wifi Calling feature, T-Mobile should provide you adequate service (both voice and data).
As far as travelling & coverage, please let us know which countries you travel the most, then we can see if there are roaming support for those regions. Good luck.