Google Nexus 6 vs iPhone 6 Plus-2

The success of the iPhone 6 and iPhone 6 Plus is continuing to pay dividends for Apple. Kantar World Panel said recently that iOS is now the most popular smartphone operating system in the United States, beating out Android for the first time since the fourth quarter of 2012. It's just barely a win, though; Kantar said that Apple's margin over Android is just 0.1 percent, meaning it's still anyone's game moving forward. Still, it's particularly noteworthy considering that Android is sold on devices manufactured by dozens of manufacturers.

According to Kantar's data, iOS has a 47.7 percent market share in the U.S., up 3.8 percent from the year-ago quarter and barely beating out Android's 47.6 percent share. Windows Phone lost 0.4 percentage points and now sits at a 3.8 percent share, followed by "other" operating systems, which own just 0.8 percent of the market. Samsung is the second most popular smartphone brand in the U.S. thanks to the success of the Galaxy S5, the research firm said.

Android is also losing ground to iOS in China, despite the popularity of local low-cost vendors such as Xiaomi.

"In Urban China, Apple iOS grew share year-on-year at the expense of Android," Kantar Worlpanel ComTech Asia director Tamsin Timpson said. "While Xiaomi remained the bestselling brand in the latest period, Apple was able to close the gap slightly, growing its share to 21.5 percent from 19 percent last year." Android still has the bulk of the market share in China, however, where it's installed on 77 percent of all smartphones.

Apple's success may be attributed to its record iPhone sales during the last quarter, too, which helped it boost share. That might be harder to maintain, particularly as a bevvy of Android smartphones are set to launch in the coming months, including the expected Galaxy S6 and HTC One (M9).