As you can see from the chart above (produced by Microsoft) Android devices have been outselling iOS devices for a couple of years now. However, many of the Android devices were barely smartphones and device sales were only half the story. The app economy was the other half of the story, and iOS was stronger here. For most startups the app economy is the more important side of the story because it’s a better proxy than device sales for revenue and customer acquisition potential.
Note that I say ‘was stronger’. As you can see from the tables below the two app ecosystems are now comparable. Judging by review numbers Android users are doing more with free apps and iOS users are doing more with paid apps, perhaps reflecting the different demographics between the platforms and the higher proportion of low end devices on Android, but on balance there isn’t much difference between the two. (Slight caveat: it would be interesting to see this analysis for total app revenue, including in-app purchases.)
Given Android’s massive volume advantage, I expect that now the app ecosystems are at parity Android will swiftly move into a clear number one position on all metrics, particularly as low end devices become more app-capable. In my experience tech early adopters still prefer Apple, by and large, so we may not feel the shift anecdotally until it is quite advanced.