You've seen the commercials. Every provider claims to have the best mobile network and they use carefully chosen wording to prove it. Sometimes it's only in certain cities or with certain plans and phones. In an effort to cut out all of the marketing fluff and fine print, PC Magazine conducts a yearly nationwide speed test among the four major carriers to determine who is definitively the fastest mobile carrier.
To nobody's surprise, Verizon was the winner yet again. What was interesting in this year's study was T-Mobile's jump to second place ahead of AT&T. They finished at only one point behind Verizon, too. PCMag's results show Verizon offered the most reliable and consistent high-speed network overall, but split individual wins for 36 cities and rural regions three ways with AT&T and T-Mobile. Tests were performed using Galaxy S8 smartphones with a customized version of the Speedtest.net software. The TL;DR is as follows:
Verizon: fastest mobile network overall
AT&T: fastest average download speeds
T-Mobile: nearly the same performance as Verizon but far cheaper
Spring: fast speeds but still playing catch up on reliability
Although only the "big four" carriers were tested, this still accounts for the vast majority of providers. Smaller carriers like Cricket, MetroPCS, Virgin, Google Fi, and Boost Mobile all reuse the big four's networks. The ongoing price war between the four carriers has definitely been beneficial to customers.
Maximum and average download speeds have consistently improved for 8 straight years. Sprint made large improvements in 2015 and 2016 but those have appeared to slow down. While Sprint does offer the same top speeds as the other providers, they are much less consistent overall.
Looking to the future, 4G will continue to advance until 5G arrives in a few years. In the meantime, carriers are investing heavily in small cells which can help fill in coverage holes and boost capacity in popular areas. Mobile network technology is relatively slow to evolve though, so don't expect gigabit download speeds to happen overnight. After all, PCMag was still testing 3G speeds up until last year.