I think it more depends on your area, where I live Verizon has the best coverage sadly. A buddy 45 min from me has T-Mo and has no issues around him, until he comes over to my place.
I was with T-mobile almost 2 months, but ran back to Att. Att loyalty gave me equal plan that T-mobile gave me with free line for my 4 lines.
I had SMS delays and problem with call routing to my other lines on my plan. I couldn’t simply call my family members. I had 3-4 texts coming the same moment from different people and different providers. When I called this people I found that the delay was 15min to 24 hours.
I still have one T-mobile line and I found that it gets even more congested in Boston and in some major airports.
I also want to add that in my area T-mobile had 2 outages in September while Att and VZW worked great.
The other reason I switched back: Att and VZW have propane/gas backup generators on my local sites, not simply batteries.
This is my true experience and I do understand that may be someone has different experience and it is based on many factors.
As others have mentioned, it depends on the area that you live. I have no issues with call quality and texts since switching to T-Mobile over two years ago. Although I have experiences some issues depending on where I travel, but for the most part, their service is very good in my area.
Been with t-mobile for about two yrs. I’m in metro Detroit (suburbs). At least with the iPhone X and XS Max and pixel 2 it’s ok. I keep WiFi calling off. I have noticed in the past 6 months or so it has improved. I made a complaint to t-mobile due to poor reception in my apartment and they provided a free signal booster. Now I have full coverage. I am thinking of switching back to att sometime this year. There jump program is a joke and the down payments are ridiculous for new phones! I do believe customer services is better though with T-mobile.
Turn off wifi calling. No matter the network, I've found cellular voice quality to always be superior -- no drops or cutouts, people sound better/clearer, and everyone says I sound great when on cellular voice. Wifi calling has sucked forever.
Also, that's a big reason Apple invented FaceTime, including FaceTime Audio. FaceTime Audio sounds better than anything else available, better than cellular, better than wifi calling.
I was with AT&T (post-paid) for over 10 years and recently switched to Mint pre-paid (T-Mobile network). The coverage in my area is not as good as AT&T, and I've definitely noticed more coverage issues than I had with AT&T, but calls and texts have been reliable, and I've had no issues with wifi calling.