Facebook got a late start, more than a year after the iPhone version.

But while tied briefly this week, the Android version of Facebook is starting to pull away from the iPhone from Apple, following the growth of the Google operating system.

AppData, which tracks such trends, was reporting late Saturday that the Android app has 58.3 million daily active users (DAU) vs. 57.4 million daily active users for the iPhone app. Facebook develops both apps.

Still, iPhone leads in MAU—monthly active users: 99.1 million vs. 85.4 million.

But Josh Constine said at TechCrunch says that DAU, or “stickiness,” the percentage of monthly active users who return daily, is the stat that counts. That’s 68.2 percent for Android compared with 57.9 percent for iPhone.

“This could indicate that Android devices appeal to a younger, more Facebook-engaged audience, or to more hard-core technology users in general. The iPhone’s role as a fashion and status symbol may be drawing less engaged users,” he says.

Another possibility is the release of an optimized iPad app in October drew some users from the iPhone column.

“Meanwhile, Facebook for Android 1.8.1’s ability to access Timeline can help the app grow its lead,” Constine says.

Android has been piling up major stats in recent weeks, such as its 10 millionth download and 200 million Android devices now in use. The 500,000 activations a month yields nearly 17 million per month, now about the same rate for iPhones per quarter.

Watch the gap continue to become even larger: 2012 is expected to bring continued growth and domination, with an estimated one million activations a day by this time next year. The Android train is pulling away.

This could have other affects. Growing popularity for Android could result in Facebook giving those users the first crack at its new products, which potentially could influence which phones Facebook fans select.