T-mobile if you want decent coverage and the best rates. Verizon if service coverage is the most important thing. Sprint is at the bottom and ATT is stuck between verizon and t-mobile. They are expensive and offer nothing over verizon.
If you believe coverage maps, and ads, sure. We were an AT&T and Verizon family for a while as my wife's phone was partially paid for by work. AT&T wipes the floor with Verizon in the New England area. Shockingly slow speeds and bad connection in general, compared to AT&T. It was worth paying an extra $20 per month to just get her on one account.
We have also made a couple cross country trips (mainly driving through the US on I-80 and once I-40) and AT&T always had as good or better reception/speeds than Verizon.
Not posting this to start a war, but I do think Verizon has done phenomenally with their marketing. For a long time their "do you hear me now?" campaign made a lot of sense, and it still resonates with people today. Real world use, IME, no longer puts Verizon as the clear winner.
I would HANDS DOWN have agreed with your assessment about 3-4 years ago though!