The race for smartphone supremacy is as close as it’s ever been, according to newly released data from The Nielsen Co., and merchants in mobile commerce or preparing to make the leap face decisions on where to focus their efforts. Of U.S. smartphones in use by adults in November, 28.6% ran Apple Inc.’s iPhone operating system, 26.1% used Research in Motion’s BlackBerry operating system and 25.8% ran Google Inc.’s Android operating system.

The iPhone is increasing market share slightly, BlackBerry is dropping and Android is growing strong. From June 2010 to November 2010, the iPhone grew from 27.9% to 28.6%, BlackBerry fell from 33.9% to 26.1% and Android rose from 15.0% to 25.8%.

One unknown may have an impact on the race this year: Apple is reportedly going to begin offering the iPhone through Verizon; to date it has only offered it through AT&T. This has the potential to boost the iPhone’s market share, and perhaps keep the mega-popular smartphone ahead of the numerous Android smartphones combined.

Retailers, consumer brand manufacturers, travel companies and ticket sellers in mobile commerce continue to focus their mobile efforts first on the iPhone, largely because of the device’s prominence not just in the mobile hardware market but in web traffic logs. But research like that from Nielsen increasingly shows that Android phone adoption puts that platform nearly on a par with the iPhone, and as traffic from Android devices increases, so, too, must the attention merchants pay to the popular operating system, m-commerce experts say.

“Apple’s seniority and the rapid rise of Android give retailers the opportunity to use platforms with advanced functionality and an increasingly broader base of mobile shoppers,” says Tom Nawara, vice president of digital strategy and design at e-commerce and m-commerce research and consulting firm Acquity Group LLC. “It’s a great opportunity for retailers right now to do more than just basic m-commerce—smartphones can help bridge the gap between the online and in-store worlds. The rapid rise of these two types of smartphones and of smartphones overall will enable the primary vehicle for retailers to address their audiences in 2011.”

Some experts, however, believe that the type of smartphone that reigns supreme is irrelevant.

“Retailers need to try to ignore the ‘hardware wars’ and think critically about who their audiences are and how they can provide the best customer experience through mobile. Hardware-specific branded apps, while great for keeping loyal customers engaged, have generally underperformed for attracting and retaining new customers,” says Rich LaPerch, CEO of mobile app and site builder Aegis Mobile. “Regardless of platform, accessing the Internet is still one of the top user activities on smartphones. That’s customers researching products and comparing prices while shopping. That means that companies offering a mobile experience should not simply migrate their PC experience but design it for the mobile user. Integration to back-end systems and business processes is where companies need to focus to ensure the best possible customer experience.”