A great illustration of the difference between iOS and Android are the way apps are delivered to each device. On iOS, your only official option is the App Store. This is the perfect example of the double-edged sword of Apple’s approach. The benefit is that Apple inspects and approves every app in their store. The downside is that Apple controls and approves every application in their store. They can, and have, rejected apps for any reason — and when they do, there’s little recourse for Apple users.
Android, on the other hand, has a market where there isn’t any real inspection process, which makes it a buyer beware free-for-all. The end user is accountable for the security of their device. If the official Android Market (recently upgraded to the Google Play Store) isn’t enough for you, there are about a half-dozen other markets that you can download apps from, as well as the ability to download apps directly via a PC or your phone and side-load them onto your device — all without any risky jail-breaking or rooting of your device. This makes it very difficult for anyone to limit what apps are available.
With Android, I also have access to the file system, so I’m able to create a Kindle document in Calibre and send it via email, download the attachment, and then copy it in the file structure on my Android device to the Kindle directory. Kindle automatically adds the new book when I load the app.