The mouse roared, the elephant lumbers forth: T-Mobile, as the distant fourth-largest carrier in the US by subscribers and revenue, needs to have a gimmick. It chose to use its limited 3G network allocation to push for the fastest possible flavor available right now. The firm went to HSPA 7.2 network wide (including backhaul support) before AT&T; AT&T is using HSPA 7.2 but says it hasn't lit it up nationally due to backhaul issues.
T-Mobile several months ago put HSPA+ (21 Mbps raw downstream) on the table, and early this year said it would have the coasts deployed by summer, most of the rest of its coverage area (which is approaching AT&T's and Sprint's) by the end of 2010. AT&T seems stuck on its HSPA 7.2 upgrade with LTE looming as the next network refresh. AT&T even said last year it wouldn't deploy HSPA+.
I guess the future revenue of LTE seems too far in the future, and AT&'s CEO said on Friday (official press release not yet on its site) that it would roll out HSPA+ apparently the 14.4 Mbps flavor) on its US network to cover locations serving 250m people by year's end.
Sprint covers north of 230m people with 3G; Verizon somewhere over 280m; T-Mobile's 3G network passes more than 200m at last check, but it has licenses to allow coverage as large as Verizon (whether that's a good return on investment is a separate question).
Verizon continues to have the short stick in this 3G/3.5G/4G competition. It's EVDO Rev. A service tops out at 3.1 Mbps, and while it will have a super-fast LTE network running with several Mbps downstream service in late 2010, comparable coverage to T-Mobile or AT&T's HSPA+ network won't come until perhaps 2012. Sprint comes in third with Clearwire planning just 120m people covered with 4G WiMax service in 2010.