Have you gotten all the features, the iPhone 5S got?
Do you have the nice blurred Control Center background?
Android's Problem is fragmentation, and it wouldn't help at all to just backport some functions to older devices, because then developers coulnd't be sure about tthe availability of any API.
My iPhone 4S benefited immensely from iOS7 (UX-feel not withstanding). The biggest difference for was in the camera software. I can't describe how much better it is performing in filming things as they happen.
By contrast, my Galaxy Nexus has become slower and slower with each upgrade. With the last update, my keyboard started to crash... I was really looking forward to the 4.4, hoping things would improve.
And yes, I use two phones and most of the time have both with me... GN is no longer used as a camera though.
Quite to the contrary, the whole point for iOS to be supported on "old" devices like iPhone 4 is reduce fragmentation: developers can focus on building for the latest iOS using the latest API and generate one binary. For god's sake, you can even target both 32-bit and 64-bit platforms with one build. You only need to deal with "availability of any API" when you hit hardware limit, like features that only work when there is Bluetooth LE or Dual Band Wi-Fi.
It's not about user-facing features. It's about the API and OS bug fixes. I upgraded my iPhone 4S from iOS 5 to iOS 7 not because I wanted iOS 7, but because I was unable to download new apps. Everyone in the App Store was already targeting exclusively iOS 6 and I didn't want to get further left behind. In the iOS world, developers target the latest and greatest API, taking advantage of new features and bug fixes. That's a good thing (tm) for users.
Contrast that with Android, where developers are still targeting Gingerbread and are unable to take advantage of any of the bug fixes in ICS, JB or KK.
