iOS is pretty much an app launcher. And that seems fine until you use an os that allows apps to extend the base functionality of the system and you realize how much more an os can be.
The variety of new keyboards available on Android is a great example. While iOS users are still pecking away like it's 2007 I have swype or swiftkey if I want them and the innovation in those apps is now making its way into core Android.
Another example - I can make Viber the default handler for all messaging, both sms and Viber messages.
I can make Firefox my default browser for everything and it's not just a wrapper around webkit.
I can share to pocket from almost any app, not just those that explicitly code for it.
When I want to attach a photo to an email I can choose from any app on the phone that provides images, not just those that the app developer found time to support.