With 14.1 million iPhones sold in the recent quarter, it makes sense that Apple is also ruling the roost in mobile ad impressions.
Apple's iPhone accounted for a 30 percent share of hardware impressions on Millennial's network, with iPhone racking up 46 percent of smartphone operating system impressions for September, compared to just 29 percent for Android.
Still, ad network Millennial Media said revenue for smartphones running Google's Android operating system actually led Apple's iPhone.
"This month, for the first time ever, Android revenue exceeded iPhone-only revenue amidst strong raw iOS impression growth," according to Millennial's Oct. 19 report.
Millennial CFO Michael Avon explained in a blog post that Millennial saw higher average fill rates, click-through rates and prices on Android applications and mobile Web inventory than on iPhone inventory last month.
"We believe this occurred because there are fewer applications available on Android than on iPhone (though the gap is narrowing), and the mix of applications available on Android is still different [from] the mix on iPhone," Avon explained. "This means less inventory to meet current advertiser demand, resulting in higher fill rates and prices."
He also thought that advertisers are paying a premium to reach new Android phone users, and he has heard from advertisers that Android allows them to reach targets across all major carriers. iPhone is still only available on AT&T.
"With more advertiser demand per each available impression on Android, it resulted in more revenue per impression," Avon added.
Meanwhile, thanks to the successful Android-based Droid phone, Motorola surpassed Samsung to become the second largest device manufacturer on the Millennial network after Apple.
Motorola accounted for a 15 percent share of impressions in September, compared to 14 percent for Samsung, whose Galaxy S Android smartphones are sure to keep the leading phone maker in the game.
Millennial said Android ad requests grew 26 percent from August to September, but are up 1,238 percent from January. Given that growth, it's understandable how Google's own mobile ad business is on pace for $1 billion for 2010.
Meanwhile, Apple ad requests grew 10 percent month-to-month and are up 18 percent since January.
Clearly, while iPhone is still enjoying a lead over Google, that lead is shrinking, thanks to Google's meteoric growth. Apple's share of the smartphone OS plot on Millennial was 70 percent in March before Android gained momentum to rise to 29 percent.
Millennial Media isn't the only one seeing the Android ascension, since comScore said Android's market share is nearly 20 percent, or within 5 percent of the iPhone's total market share.