T-Mobile is extremely adept at misleading advertising and it has left a very bad taste in my mouth. Beyond that, I have Verizon and AT&T towers at work, so it would be silly to not get one of them.
I think out of these three, T-Mobile is the best. Your own example demonstrates it. Anyway, it was always the only sensible option for users of N900, N9 and so on.
On the contrary, my example, that I have AT&T and Verizon towers at work, is that T-Mobile has less coverage.
They also started the entire anti-net neutral trend with throttling video, zero rating content from specific providers, etc. Which the others carriers were unfortunately all too willing to copy.
It is hard to see from either a technical or ethical standpoint how T-Mobile is better.
Verizon and AT&T were anti-net neutrality long before T-Mobile were. I'm not defending what they are doing wrong. Just pointing out, that you if you want to have your own unlocked device, they are the best option.
