Android apps that you purchase will work on products from Google (Nexus), Samsung, HTC, LG, and other companies. iOS apps that you purchase will only work on products from Apple.
I think this only tells part of the story - You are still being locked in to google ecosystem, (to access Google Play) and manufacturers of those phones need to pay Google for certification eg
I don't think Android is a good example of a free OS any more anyway. In comparison to iOS, Android is "more free" but it still used by Google to mistreat its users. Aside from freedom aspects, Android is very much a part of the anti-privacy upload-everything-to-the-cloud cartel. I was shocked to find out how many smartphone devices are literally bricks until they are remotely activated upon registration. Not sure if Android devices do this yet, but Windows Phone does, and I heard iOS does it as well. Replicant along with the F-Droid app store is a far better example of a mobile operating system which attempts to provide software freedom for users, although its actual use is quite limited, even more so than GNU/Linux on desktops and laptops. (See http://www.replicant.us and https://f-droid.org for more information on these projects). I've never owned a smartphone or tablet so I don't have any comments on the practical aspects of those devices. -- Andrew Roffey http://andrew.roffey.org [mailto|xmpp]:andrew@roffey.org see website for GPG/OTR pubkeys