Android has twice the smartphone marketshare than iOS. But, it is so fragmented that building for the Android market requires you to have at least few different devices to test out your app, not to mention that there are multiple versions of Android and modified Android from the network providers. It definitely requires more effort than building for iOS.

App distribution on Android is actually more tricky than the App Store on iOS. There are actually a few "App Stores" for the Android, Google Play vs Amazon App Store.