I think you're both right. I have been a T-Mobile customer for 10+ years. I have probably better coverage while in a city, like Boston, than anyone I know.
I also have some pretty bad coverage when I go up to Vermont.
So, if you stay in the cities. Excellent Coverage.
Roam into the rural world: Spotty coverage.
Fact, though, even AT&T's coverage in some of these same locations is pretty poor. Verizon seems to work best.
Re: Vermont -> I had no T-Mo coverage at all in southern Vermont, specifically Brattleboro, which is in the extreme southern part of the state and not far from civilization. Out here in eastern Washington I've had pretty good coverage (though I AM on the I90 corridor - civilization again, relatively speaking) and am a happy camper on their $30/mo, 100min, 5G Walmart plan.
I also have some pretty bad coverage when I go up to Vermont.
So, if you stay in the cities. Excellent Coverage. Roam into the rural world: Spotty coverage.
Fact, though, even AT&T's coverage in some of these same locations is pretty poor. Verizon seems to work best.