The latest study of network performance by testing firm RootMetrics delivered one result that shouldn't surprise people who've spent much time testing 5G phones and hotspots – and another result that might raise a few eyebrows.

The report, released Thursday, credited T-Mobile with the best 5G availability in 45 markets tested but gave an overall nod to AT&T for superior 5G download speeds and reliability.

"AT&T led the competition, delivering a combination of the fastest worst-case, median, and best-case 5G download speeds together in 14 cities," the report summed up. "T-Mobile registered the fastest speeds across all three metrics in six markets, while Verizon did so in three cities."

The RootMetrics report noted that T-Mobile was the only carrier out of the big three to offer 5G in all of the 45 cities it tested, while AT&T offered it in 44 and Verizon in 43. The most recent nationwide RootMetrics report, released in February, also found that T-Mobile had "the largest 5G footprint of any carrier."

But Thursday's study judged AT&T to offer a slightly more reliable 5G service – both in terms of connecting to a 5G signal and staying on it – than either of its rivals.

Further, RootMetrics found that AT&T's 5G was faster overall, delivering median download speeds of 50 to 100 Mbit/s in 31 markets; T-Mobile only did that in 11 markets and Verizon did in ten. The study also complimented AT&T for providing a higher floor, in the sense of its 5th-percentile speeds being faster than T-Mobile and Verizon's.

The report does note that in the smaller universe of best-case results (meaning those in the 95th percentile), T-Mobile far outstripped AT&T and Verizon, offering downloads of 200 Mbit/s or faster in 27 cities, versus four in each for its rivals.

It does not, however, offer a median or average number for all of these tests.

T-Mobile's unique midband 5G, deployed on the 2.5GHz spectrum it inherited from Sprint, offers much faster speeds than the lowband 5G in service at all three carriers while covering far more territory than their millimeter-wave 5G service.

Other studies have ranked T-Mobile faster; in January, Opensignal found that T-Mobile had the fastest 5G service in America.

That may reflect differences in methodology. RootMetrics does automated testing on particular phones carried by testers along walking and driving routes, while Opensignal relies on crowdsourced data from millions of copies of its apps on consumer devices.

It may also reflect where RootMetrics did this latest round of testing. Of the 45 cities covered in this study, only three (Phoenix, San Antonio and San Jose) ranked in the ten most populous US cities, with another three (Jacksonville, Columbus and Denver) filling out the top 20. A full 32 of these cities don't make the top 50 US cities by population.

That's unlikely to amuse T-Mobile, which has a history of objecting to RootMetrics rankings that place it below competitors. Nor is this report likely to settle any industry squabbles over who has the fastest 5G.

— Rob Pegoraro, special to Light Reading. Follow him @robpegoraro.