Does it make sense to build for iOS or Android first?

I think you should program for iOS first. Think about a company like Instagram, they made the app for only iPhone users, then it became popular. Once the app was released for Android, millions of people downloaded it in less than 24 hours. In my opinion iOS apps gets more attention then Android apps. Android apps aren't a bad place to start though, there are some really good Android apps I use everyday.

It should depend on the type of app you're building. If the monetization is important (e.g., it's a paid app), then I hear that iOS is still the way to go. (As kavalec points out, the trend is slowly changing though.) If it's important for you to have wide distribution of the app, then Android has a larger reach and this will only increase over time.

1. The trend seems to be towards Android.

2. Apple seems to be making more, not less, difficult to code iPhone apps.

Totally iOS. (1) Non-trivial Android development is much more difficult due to fragmentation and random bugs, (2) in AppStore, your chances of at least breaking even are way higher than in Google Play.