Which really you're supposed to be doing on both OSs at this point. As an iPhone user there are still apps that don't support the 6 size screen and it's obnoxious.
iOS has four different retina screen resolutions on the phones, more on the tablets. For all we know there will be more in two weeks. Creating pixel perfect layout doesn't work very well anymore.
It may be easier to exhaustively test on iOS because there aren't quite as many variations, but devs should definitely be using flexible layouts.
And then of course there's accessibility. If your app is already designed to handle different screen sizes then it's easier to resize various elements because you want to bigger or smaller text.
iOS has four different retina screen resolutions on the phones, more on the tablets. For all we know there will be more in two weeks. Creating pixel perfect layout doesn't work very well anymore.
It may be easier to exhaustively test on iOS because there aren't quite as many variations, but devs should definitely be using flexible layouts.