Market share? It's been shown that even though a lot of "android" devices may be out there, the majority of use and engagement from mobile platforms is still coming from iOS.

See this post on asymco:

http://www.asymco.com/2012/11/26/the-android-engagement-para...

For many markets (probably globally too?), there's no single smartphone that's more popular than the latest iPhone. So if you're only going to put one device in a photo, that'll probably be it.

And if you look only at the demographics you're interested in, it's likely that iOS will be at or near the top anyway.