Why is this the case? Could the issues that early upgraders faced scared others off? Is it because the iPhone 4S - which has been reported to perform poorly under the new version putting off upgraders - and earlier incompatible iPhones make up a larger percentage of the iOS community than first thought?
Either way it's hardly a terrible position for Apple to be in - KitKat is currently only used by 25% of the Android community. Interestingly though, that 47% of the iOS community of 400m (188m) is substantially less than the 25% of the Android community of 1bn (250m).
So there are more smartphones running the latest version of Android than iPhones running the latest version of iOS.