If you’re looking to handicap which iPhone carrier is ahead in the LTE horse race, one Wall Street analyst points to Verizon and Sprint as the big winner and loser. Indeed, an LTE-enabled iPhone 5 would “change everything,” making it “the biggest consumer product launch ever.”

Jeffries & Co.’s analyst Thomas Seitz Thursday advised investors to buy Verizon shares, hold onto AT&T and sell Sprint-Nextel. Verizon now has 230 million LTE POPs — more than all other US carriers combined. As a result, Seitz sees “a share shift towards Verizon, primarily at AT&T’s expense.”

AT&T’s percentage of iPhone users could drop to 45 percent, down slightly from 47 percent. Additionally, around 9 million subscribers locked into the carrier could switch to Verizon, he said. In the meantime, T-Mobile — which AT&T tried and failed to snap up — is a wildcard, Seitz writes.

“If T-Mobile were to get the iPhone, we believe Sprint will face competition for iPhone subscribers at the low end of the postpaid market. “In our view, AT&T and Verizon could lose some subscribers to T-Mobile,” however the number would likely be small, he adds.

Of course, all of this hinges on the iPhone 5. Seitz agrees with the predominate expectation that Apple will unveil the new handset on Sept. 12, followed by general availability September 21. Up to 5 million iPhone 5 will be sold by the end of September, with another 15 million purchased in time for Christmas, according to the analyst.