Moto G is the best sub $200 new, off-contract phone period.
The HTC One is an excellent phone and for $179 on-contract, it isn't a bad deal.
You could also purchase any used GSM-based phone for a decent price and pop in the T-Mobile SIM.
I think LTE is sort of overrated. I use LTE a lot, and for most tasks, 3G can handle everything short of streaming Netflix and videos quickly.
For $350, the Moto X is a great off-contract phone. But the Nexus 5 is also the same price and has a superior SoC and display.
If its your first smartphone, I would get the Moto G. It will be off-contract so a lot of upgrade pressure is instantly removed.
If you've already had a smartphone and want a significant upgrade, I would look at the Nexus 5, or used Nexus 4's. The HTC One is also a good choice, but being on contract is a rather crappy outlook for many technology enthusiasts on this site.