Well these are confusing results: T-Mobile is first in OpenSignal and last with Root Metrics. Makes some sense if you think about it. One is weighted by people. So there is a bias where most people are on the cities. Root metrics is by region. So the best plan would be to use t-mobile mainly and have a Verizon prepaid sim for rural trips. Kind of the way we currently use google fi overseas right now to augment Verizon. But this is even cheaper given t-mobile pricing and free international. U might only need Verizon once or twice a year.
https://arstechnica.com/information-technology/2017/02/t-mobile-wants-you-to-ignore-last-place-finish-in-nationwide-network-test/