I come across a great article which outlines iOS Updates and support for their devices versus Android.
Some of the major highlights for me are:
- Some devices on day one, were a major release behind
- All phones aside from the Nexus range were being sold with an out of date OS
If you which to read the full article and how everything was caluclated take a look over at http://www.fidlee.com/android-support-vs-ios-support. Would be great to see it include tablets in future updates/revisions.