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Ever since Sprint (s s) launched its Evo with WiMAX last year, calling it the nation’s first 4G phone, competing operators have scrambled to use the 4G moniker for their own devices and services. T-Mobile soon began touting that its HSPA+ network upgrades would bring “4G-like speeds” and now simply uses the 4G tag for phones that have 14 Mbps or better radios. AT&T (s t) is currently in the process of similar HSPA+ upgrade and has used 4G in the name of recent handsets, such as the Motorola Atrix 4G (s mmi) and HTC Inspire 4G. And in December, Verizon (s vz) launched its own 4G network upgrade in the form of LTE, which is different from HSPA+ and WiMAX.

As this point, 4G is more of a marketing term than anything else for the carriers because technically, none of the current solutions meet the initial International Telecommunications Union definition of 4G. However, the ITU backtracked a bit because it realized all these mobile broadband networks offer speeds that are noticeably faster than 3G networks. That helps the marketers, but what does it mean to consumers? Would the 4G service from one carrier be comparable to that from another? The best way to answer that question is to test each carrier’s 4G service in one geographic area, and that’s exactly what RootMetrics did in Seattle, Wash.; the detailed results of which you can see here.

I first saw the company’s innovative mobile app last January. It crowdsources both the quality of service and mobile broadband bandwidth speeds, making it an excellent tool to test the 4G claims of each major carrier. Earlier this month, RootMetrics put the networks to the test and clearly, not all 4G networks are equal. Verizon’s LTE network in Seattle performed much as I found it in my local area: extremely fast and reliable. One could argue that few are on the network, which is a valid point, but regardless, the carrier is delivering as advertised, with an average download speed of more than 17 Mbps and 100 percent availability in Root’s testing.

Sprint’s WiMAX and T-Mobile’s HSPA+ were found to deliver fairly comparable downloads of 4.4 Mbps with the data availability ranging from 80 to 90 percent for both. T-Mobile’s service fared better on the upload side, however, providing more than double that of Sprint’s 605 Kbps on WiMAX. AT&T doesn’t yet show Seattle as a 4G city — the current coverage maps I found show about 10 cities with 4G — so it’s no surprise that a 4G handset in Root’s testing indicated the slowest speeds. Downloads on AT&T averaged 1.1 Mbps, which are indicative of 3G throughput; even with a 4G phone. Those are the high-level results, but this graph showing which carrier delivers what speeds at various intervals brings further detail to the picture.

It’s certainly true that mobile broadband performance is affected by many factors: location and cell tower proximity, the number of users in a given cell area, and the speed of the wired backhaul that provides connectivity from the tower to the web. But all carriers face those challenges and yet all deliver a widely different level of service even while marketing the mobile broadband as 4G. Maybe the ITU should have stuck to its guns?