As someone up thread said, if your model depends on ad revenue (in app ads), then Android. If it's app purchase revenue, then Apple.
Which also makes your statement true. If you're not buying apps for the Android, you have nothing tying you to the platform. If something new comes along, you'll jump to the new sparkly because you have no money invested. With Apple, you're buying apps. So you're throwing away the money you've paid.
I have quite a few apps on my iPhone that I would have more of a problem bailing on because I've paid for them vs my Android phone that I'd punt in a hot second and without a second thought. Same as the Blackberry I used to have. The benefit was the physical keyboard but other than that, no reason to keep the BB around once I got the iPhone.
[John]