I've had all the major carriers over the last decade. I live in northern NJ and found that leaving my home town the various carriers' service varied greatly. I currently have 4 lines on Verizon, all unlimited talk/text/data, and pay $196 per month all in. I have Verizon FiOS for TV and internet, plus Verizon service for home phones. The old "Triple Play."
Sprint: Unreasonably awful. Almost like they were not even trying. Outside of major metro areas Sprint has no footprint. My neighbor worked for Sprint helping build out their network. Sprint worked hard to improve but simply fell flat on their face. I'm shocked that T-Mobile bought them. The move to 4G LTE and 5G is the only thing that makes it possible. I recall Sprint buying Nextel and what a disaster that was. $33 Billion for the purchase, and a couple years later they simply wrote it off. One giant pile of fail and a "never mind".
T-Mobile: Good speed and prices, but if you wander outside of major cities they fall down. Lots of dropped calls and slow data speeds.
AT&T: Great speed, middle of the road prices, good network footprint, but their customer service was poor and they loved to nickel and dime customers with all kinds of extra fees and charges. Still, their service was a big improvement over T-Mobile.
Verizon: Best network coverage I've found. Data speeds are good to very good. One issue I've had with Verizon is how they abandon old phones and disallow them on their network. Once they decide to pull the plug on a range of devices you're just screwed. No concessions to customers with an orphaned device. They're still the most expensive carrier but it's a lot closer than in days past.