T-mobile here for personal use, Verizon for work.

T-mobile: Best darn CS I've ever encountered. Very fair rate plans too IMO. Their coverage is still a little weak in our area, but it's improving and I'm willing to make the trade-off for the good CS.

Verizon: Awful CS. I occasionally need to deal with them about our work phones, and getting anyone to help me is like pulling teeth. However, they have the best network in our area, hands-down. That said, I'm not willing to pay their prices and deal with the CS nonsense for better coverage.