AIO = ATT. ATT & T-Mobile both roam on each other. if you weren't getting coverage for one of those carriers in a location, chances are that you won't get it from the other either. remote towers have very little capacity for obvious reasons.
Do they roam HSPA+ and LTE? Their coverage maps are pretty drastically different. Tmobile has "no coverage" where ATT still has some. Just assumptions at this point, I guess.
Which AIO plan are you looking at? looks like they have 55$ net with throttling after 2GB. Consider straight talk with an ATT LTE sim which is net 50$ with throttling after 2.5GB.
actually for any plan, AIO seems to have no advantage over straight talk, epsecially considering you are using the same network.
I'll get the 7 GB and the wife will get the 2 GB. Besides, have you read any of the reviews? They sound horrible. Also, AIO throttles you to 256 Kbps, which is still usable. Straight Talk throttles it to unusable speeds and most times keeps you there forever, from what I gather. I'll pass on that.