In other words, none of the three carriers is expected to have a significant advantage over the other, although Apple will clearly benefit, according to an analysis by online tracking and analytics firm comScore.
However, comScore said Sprint could gain a "significant advantage" over Verizon and AT&T in iPhone sales if it offers an iPhone with its unlimited data plan, making it the only one of the three to do so.
ComScore also noted that Verizon has the highest customer satisfaction rating among wireless operators, which will matter to new iPhone customers if all the carriers price the iPhone 5 handset competitively.
AT&T, which at one time was the only carrier that provided iPhone wireless service, could maintain some advantage over Sprint and Verizon if it continues to sell the older iPhone 3GS at the bargain basement price of $49, as it also sells the iPhone 4 and iPhone 5. (ComScore said this expectation makes sense if Sprint and Verizon sell both the iPhone 4 and iPhone 5).
"AT&T will continue to have an edge in terms of product breadth, with the ability to sell the iPhone 3GS at a discounted price," ComScore said.
In fact, ComScore found in a July survey that AT&T had 82% of iPhone customers, while Verizon had 15%. AT&T had such an advantage from selling the iPhone 3GS at a low price, but also because it sold the original iPhone exclusively starting in 2007. Verizon didn't start selling the iPhone 4 on its CDMA network until February .
ComScore also noted a surge in U.S. buyers of iPhones in the past year coming from households that make less than $50,000.
Given the various advantages for each of the three carriers, ComScore concluded: "The many issues at play do not point to a clear winner for the wireless operators" from all three selling the iPhone 5.
"The one clear winner so far would appear to be Apple, which stands to gain market share from the additional market sectors penetrated by Sprint and providing another device option for customers of AT&T and Verizon," ComScore added. Sprint's strong base of customers in the Midwest could give Apple increased market penetration in that region.
According to ComScore's July figures, 42% of U.S. smartphone subscribers used smartphones running the Android mobile OS, while 27% had iPhones.
ComScore's analysis is based on a survey of more than 30,000 U.S. mobile phone subscribers.
Other analysts said the nuances of Sprint's iPhone rollout are difficult to measure. For example, if the iPhone 5 is released on the HSPA+ network standard, it won't help Sprint, which offers its CDMA and WiMax networks, but not HSPA+. That means Sprint would have to sell an older version of the iPhone that could run on its networks, said Jack Gold, an analyst at J. Gold Associates.
"Sprint could heavily discount [iPhone 4 on CDMA], but the halo effect of the latest devices will not be there and they'll be perceived as the bargain store," Gold said.
Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at @matthamblen or subscribe to Matt's RSS feed . His e-mail address is email@example.com .
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This story, "If Sprint becomes third iPhone carrier, how much does it gain?" was originally published by Computerworld.