OK, this is the fastest wireless carrier in the nation

Two weeks after one testing firm crowned T-Mobile the speed king, a new study claims rival Verizon actually has the superior network.

Cellular towers from Verizon helped it win RootMetrics' study for a fifth straight time.

James Martin/CNET

T-Mobile may need to postpone taking a victory lap as the fastest wireless carrier.

Verizon Wireless took the top honors in a new study conducted by testing firm RootMetrics, which broke down its findings by states, metro areas and categories including network speed and call reliability.

In virtually all segments, Verizon proved dominant. It's the fifth straight time the New York-based carrier has emerged as the top dog in RootMetrics' semiannual study.

The results add an interesting counterpoint to the conclusions drawn by rival testing firm OpenSignal, which crowned T-Mobile the nation's wireless speed king just two weeks ago.

These tests are significant because they serve as the basis for many of the ads you see, with one carrier or another touting the most reliable or the fastest coverage. While the carriers are more often competing for your business by offering discounts and promotional benefits, the aura of network superiority and the promise of better coverage remain huge factors in which carrier to choose.

The different results stem from how each firm conducts its study. RootMetrics sends vans and professional testers throughout the nation, claiming that is the best way to get comprehensive results. OpenSignal uses crowd-sourced information through apps downloaded by consumers, which it argues offers real-world data that's more up-to-date.

Verizon swept nearly all six categories in the RootMetrics appraisal. On a nationwide basis, Verizon was ranked No. 1 in overall performance, network reliability, network speed, data reliability and speed, and call reliability. Verizon tied with AT&T on reliability and speed of text messages. Verizon also took the most first-places finishes in those categories on the state and city levels.

RootMetrics

T-Mobile was often ranked fourth in many of the categories.

The discrepancy in the testing lies in the breadth of the studies. T-Mobile has concentrated its network investment in big cities and surrounding neighborhoods but tends to do poorly in rural areas. Verizon and AT&T generally have more consistent coverage across the entire nation, although T-Mobile and Sprint are catching up.

T-Mobile questioned the results, claiming that RootMetrics shut off its voice-over-LTE feature. It also repeated the criticism that RootMetrics uses older data because its tests were conducted over the last half of 2015.

"I don't know what to make of it," T-Mobile Chief Operating Officer Mike Sievert said in an interview.

RootMetrics said it did not test voice-over-LTE because it wasn't what most consumers experience with carriers. The firm did say it would incorporate the feature into its next study. "We are taking a wait-and-see approach to what the impact may (or may not be) for T-Mobile," the firm said in a statement.

Verizon took the report in stride.

"We're not perfect, so we celebrated the clean sweep for a hot second, and now we're back to work because wireless customers want a better experience every day," a Verizon spokesman said.

Sprint, meanwhile, saw improvement in its scores for call and text performance and edged out AT&T for second place for calls.

"We're encouraged to see that our network has continued to improve," said Sprint Chief Technology Officer John Saw.

The company still lagged behind in network speed and data performance.

AT&T, meanwhile, placed second in many of the categories. "We'll continue investing to give our customers the best possible experience," the company said.

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