T-Mobile USA and AT&T finished top in their classes for 3G and 4G network performance, respectively, according to this year’s PCWorld report that measures wireless network performance.

The study involved snapshot measurements of wireless service in 13 cities – Atlanta, Boston, Chicago, Dallas, Denver, Las Vegas, Los Angeles, New Orleans, New York, San Francisco, San Jose, Seattle and Washington, D.C. – across the country to get a real-time view of how the 3G-to-4G transition is progressing, and of which companies are currently delivering on the promised faster speeds.

According to the report, AT&T’s 4G LTE network delivered the fastest download speeds (9.56 Mbps) when compared with Verizon Wireless’ LTE network (7.53 Mbps), T-Mobile’s HSPA+ 42 network (5.54 Mbps) and Sprint’s WiMAX network (2.81 Mbps).

T-Mobile’s HSPA+ 21 network took the crown on the 3G side, reaching average download speeds of 3.84 Mbps across all test markets. AT&T’s HSPA+ network, which PCWorld categorized as 3G for this report, came in a close second with average download speeds of 2.62 Mbps, followed by Verizon Wireless (1.05 Mbps) and Sprint (0.59 Mbps).

On the whole, average download speeds increased, as did the number of subscribers on the networks, leading to the conclusion that operators really are meeting the growing demand for data.

PCWorld called AT&T's pairing of 4G LTE service and 3G-equivalent HSPA+ service “compelling” because customers fall back from LTE to the carrier’s HSPA+ network, which proved faster than Verizon Wireless’ standard 3G network.

AT&T’s John Donovan, senior executive vice president of technology and network operations, said the carrier made a strategic decision to roll out ongoing upgrades to its 3G network on the way to LTE.

“It’s great to see the results of our 4G network strategy in PCWorld’s tests and in the feedback we’re getting from our customers,” Donovan said.

Verizon Wireless’ LTE network, which launched long before AT&T, is way ahead on coverage. The carrier has deployed LTE in at least 203 cities nationwide, while AT&T’s LTE network is currently up and running in only 31 cities.

Verizon Wireless was dismissive of the PCWorld report, saying that speed is only one facet of service.

Tom Pica, a spokesman for Verizon Wireless, cited a recent report by Root Metrics posted at GigaOM as a more holistic picture of network performance. Root Metrics acknowledged that AT&T’s LTE service was indeed faster on the downlink in its tests, but it also noted that Verizon offers a more mature LTE network. Taking into consideration 15 total markets where both AT&T and Verizon Wireless’ LTE networks are present, Root Metrics found LTE service available during 92 percent of its download tests with Verizon, and only 66 percent of the time with AT&T.

Root Metrics also found that while AT&T may have seen faster LTE speeds, users could expect to see speeds above 5 Mbps more often with Verizon. In its tests, Verizon exceeded 5 Mbps during 82 percent of download tests and 66 percent of upload tests. AT&T surpassed this number in only 68 percent of download tests and 40 percent of upload tests.

An official statement from Verizon Wireless issued in response to the PCWorld study stated that the debate over 3G and 4G technologies will soon be over.

“By next year, our 4G LTE network will cover virtually the entire U.S., rendering the overstated 4G vs. 3G coverage discussion moot,” the statement said.

But with all the back and forth among the big guys, might we have overlooked the strong showing by T-Mobile, which consistently embraces what it calls its “challenger position”? With lower-priced, more flexible plans and fast, reliable 3G and HSPA+ 42 networks, it might be the little carrier that could. Unfortunately, T-Mobile’s HSPA+ 42 service is currently available in only 13 cities.