T-Mobile, not Verizon, will be the next carrier to get Apple’s smartphone, says an analyst

Like most analysts, Kaufman Bros. Shaw Wu believes Apple AAPL will eventually end its exclusive relationship with AT&T T and give the iPhone to other U.S. carriers — by 2011, most likely, and perhaps as early as this fall.

But unlike most analysts, who are rooting for Verizon VZ , he believes T-Mobile DT will be the next carrier to get the device.

In a note to clients, he ticks off the reasons:

  • Like AT&T, T-Mobile runs a GSM network, although on different frequencies. T-Mobile’s 3G network runs on 1700 MHz and 2100 MHz while AT&T supports 850 MHz and 1900 MHz. “Interestingly,” Wu writes, “both the new iPhone 4 and iPhone 3GS support 3G at the 2100 MHz frequency.”  Verizon and Sprint S run CDMA networks, which would require Apple building a special iPhone.
  • Apple needs another carrier to compete with Google. Google’s GOOG Android is still a niche product, with a 9% U.S. market share, but according to Wu it is growing strongest where the iPhone is not available.
  • Verizon isn’t the only show in town. Although it is the largest U.S. carrier, with 93 million subscribers, AT&T comes in second at 87 million, Sprint at 47 million, and T-Mobile at 34 million. Says Wu: “It is notable that signing up both T-Mobile and Sprint would almost be the equivalent of signing VZ.”

Wu is sticking with his “buy” recommendation on Apple with a price target of $320 a share.

[Follow Philip Elmer-DeWitt on Twitter @philiped]