With blackberry and MS having a negligible portion of the smartphone market, I would be surprised if it *wasn't* android.
About 15% of smartphone users who by a Samsung (Android) handset come from iOS users. A higher percentage of iOS users are previous Android users (about 2:1 vs those switching from iOS to Android), but there are more Android users overall, so I'm not certain that there's a net loss in the Android userbase. For example: there were about 200 million iOS devices sold in 2014, and about 1 billion Android devices. If 20% of new iOS users are former Android users, that's 40 Million switching to iOS. If 5% of Android users are former iOS users, that's 50 Million switching to Android. That's a net +10M for Android.
(some stats: http://www.dailymail.co.uk/sci...)