Should I develop an App for iOS or Android first?

I think it depends on a number of factors:

Which primary development kit are you more familiar with, Java (Android) or Objective-C (Mac)?

Android has more users on its devices, but Apple have a loyal following and all the cutting edge apps in terms of design, user experience and concept are always iOS first.

Android is often considered a more challenging platform to build for, whereas iOS has a tidy framework (Cocoa touch) based on years of expert Mac development.