I'm a big user of Pocket Casts and got to following Russell Ivanovic's (one of the developers) blog. He has a couple of interesting posts on screen sizes.
His position is that the various screen sizes aren't a big deal so long as there are relatively few different proportions. You can make different resolution objects that the operating system can select from and present appropriately.
Here's his chart of the various Android screen proportions.
Now who hasn't heard that varying screen sizes are more of a problem on Android than on iOS?
From his follow on blog post here's the equivalent chart for iOS.
Note that the iOS chart was done with guesses of the iPhone 6 screen sizes and the guessed size of the iPhone 6+ was incorrect.
You decide which would be easier to code for.