The debate between iOS and Android has been done to death and still goes on. Which of the two is better or is right to you has been discussed to death. Eventually it comes down to rocks and rules your boat as both the platforms have things that are unique as well as interesting. However, one thing that everyone agrees upon which is a burning issue for those on Android is the issue of fragmentation.
Fragmentation simply put, means that not all devices which run Android run the same version of Android. The adoption rate on iOS is without a doubt much higher given that Apple controls the hardware and software. Google on the other hand has never been a hardware company and given that most OEMs have a skin which takes time to be customized when a new Android version is released. As a result if you have an iPhone or an iPad, you are bound to have at least the option of getting the latest updates on your device.
However, to get a fair idea, you can see the chart above which shows that plenty of people rocking Android are still on lesser versions with no support; whereas with iOS you see more than 60% people are on iOS 7 which is the latest software update.