Apple's iPhone and Research in Motion's BlackBerry are in a dead heat for U.S. smartphone ownership honors, Nielsen said today.
But the iPhone's iOS was the clear winner when American smartphone owners were asked which mobile operating system they'd pick for their next device, the measurement company added.
Of the nearly 30% of mobile subscribers who own a smartphone, 27.9% said they had an iPhone, while 27.4% said they used a BlackBerry from RIM, a too-close-to-call race that Nielsen dubbed a "statistical dead heat."
Google's Android operating system powers the phones of 22.7% of smartphone owners, while Microsoft's mobile OS -- the latest is Windows Phone 7, which has only recently started to appear on new handsets -- trails with 14%.
However, Apple's iOS trounced RIM's operating system for the BlackBerry when smartphone owners likely to upgrade to a new phone were asked which OS they'd select. Nearly a third of U.S. mobile subscribers -- 30% -- said they wanted iOS, while just 13% said they'd choose BlackBerry.
Android snapped up second place with a strong 28% vote from prospective smartphone upgraders.
"Apple's iPhone and devices with the Android operating system were the 'most desired' among likely smartphone upgraders, with Apple showing a slight lead among those ages 55 [and older], 18-24, and 25-34," said Nielsen in a post to its data-centric nielsenwire blog.
Android edged iOS in the 35-54 age bracket, however, by 27.4% to 26.4%.
Google's OS is the preferred pick by U.S. users who now own a so-called "feature" phone, the term now applied to non-smartphones. Feature phones make up the bulk of the current market, with seven out of 10 mobile subscribers still using one of the less-expensive, less-capable devices.
Although a quarter of feature phone owners planning to upgrade didn't know what smartphone operating system they want -- nearly twice the percentage of undecided smartphones users -- 28% picked Android as their first choice, while 25% pegged iOS. RIM was a distant third with 11%.
Microsoft clearly has its work cut out, according to Nielsen, which said the surveys found that only 5% of current smartphone owners would select a Windows-powered handset. Slightly more, or 7%, of feature phone owners said they would go with Microsoft's mobile operating system.
Nielsen's results differed from earlier estimates by technology research companies such as Gartner and IDC, which have said Android would end the year as the world's second-best-selling mobile operating system, behind Nokia's Symbian.
But while Gartner and IDC highlighted sales and drew their numbers from around the world, Nielsen's market share figures reflected only the U.S. installed base. There, the iPhone and its iOS have a two-year head start over Android smartphones, which began selling briskly only last year.
According to Gartner, Apple's iOS will finish 2010 as fourth in global sales.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is firstname.lastname@example.org.