App Annie:

While Google Play reached close to 90% of the iOS App Store downloads in Q1 2013, the iOS App Store maintained its strong lead in monetization, earning about 2.6x the app revenue of Google Play.

App Annie notes that the revenue difference was more like 4x in 2012, so it’s closing in, but still way, way off given the near-parity in download traffic.

Bottom line: if you want to actually make money, iOS still seems like the safer bet.