In AdMob’s April metrics, the iPhone OS still lords it over the competition. Despite the growing number of Android-powered devices in the market, the iPhone remains at the top spot both in the US and international market as far as AdMob’s network is concerned. According to their estimates, there are roughly 10.7 million iPhone units in use in the US while there are only just 8.7 million Android phones in the region. In the worldwide arena, the disparate is more evident. There are an estimated 27.4 million iPhones in use which is a stark contrast to Android devices which is just roughly 11.6 million.

AdMob April 2010 Metrics: iPhone vs Android

Android appears to be a popular choice in the US which explains why it’s more competitive in the country. 75% of Android phones sold are in the US. Asia is next with 12% and Western Europe with 11%. The iPhone, as expected, is a favorite too in the North America country. 49% of the global iPhone market belongs to US with Western Europe a distant second with 28% and Asia at 14%.

As far as ad requests are concerned, the iPhone OS is no. 1 in the global scene with 42%. Android is no. 2 with 25% while Nokia's Symbian and RIM are at third and fourth place with 2% and 1% respectively. However, in the US, the story is different. Android took top honors with 46% while the iPhone OS settled for second with 38%. RIM is in third place with 7% and Palm’s webOS is still making its presence felt with 3%. For number crunchers out there, you can download the full report here (PDF).

An interesting rivalry we have here between Android and the iPhone which will surely intensify more as the months go by with Apple expected to announced the new iPhone next month and the new breed of Android phones set to roll out later this year with even more mouthwatering features.