This is a regular discussion that happens under every article on The Verge about some new iOS app. So far they are all flames thrown at each camp. This poster had a really good answer with good supporting facts. I thought it was worth sharing:

It’s not “gibberish” – it’s fact:

1. Android users spend less time with apps. http://www.businessinsider.com/android-users-use-apps-less-2013-6
2. Android users are less likely to pay for apps: http://phandroid.com/2013/07/19/free-apps-android-users/
3. Android users don’t buy stuff with their mobile devices as much: http://bgr.com/2013/12/02/ios-android-black-friday-online-shopping/

There is a meaningful difference, and if you’re trying to make money in the mobile world, you start with iOS.

Taken from the http://www.theverge.com/2013/12/5/5178432/best-new-apps-level

The only thing I'll add to this is the ease of building and maintaining apps due to a more consistent group of devices with users who upgrade to new versions of the OS regularly.

Don't mistake this for developers not succeeding on Android. That is not true -- plenty of developers make a good living out of Android.