T-Mobile has the fastest 4G in the US, although Verizon has the best coverage: latest research
Opensignal is a body set up to assess cellular data services and coverage in the US. It does so through its "active [country-wide] userbase of over 1.4 million unique devices", which gather data via the company's apps and those of its partners. Unlike many other cell-data tests, this system is automated, which, as Opensignal asserts, prevents the biases to which self-initiated consumer tests may be subject, while promoting accuracy and generating service quality-related results that are as "real-world" as possible.
The latest study incorporating this system was conducted between March 16 2019, and June 13 2019. Its results are based on over 5.6 billion measurements collected during that time. Opensignal reported that, of all the US carriers involved, Verizon had the best 4G coverage. Then again, every other major player in this test also exhibited appreciable levels of coverage: AT&T and Sprint, despite coming last in these terms, still achieved a score of just under 90%.
T-Mobile posted the best average scores in terms of 4G upload and download experiences. Opensignal also found that video streaming (which the body scores on a scale of 0 to 100) on these networks improved in this study compared to 2018. For example, Verizon fell into the 55-65 range on the scale, whereas it could not get out of the 40-55 sub-scale last year.
All in all, Opensignal concluded that the appreciable levels of 4G investment in the US as of late have paid off in terms of service experience. The group also found that the "5G era" has perhaps not kicked off in earnest quite yet: its adoption rates are still only "ramping up" at present.