Re:Apps will be the determinant
>Since we want to use standard off-the-shelf products our choices are being determined by manufacturer policies.
>I believe, eventually, this and App availability will determine the dominating OS and, at present, that appears to favour Android.
Except that for in-house apps, the enterprise license explicitly provides a mechanism for developing and deploying apps to corporate devices without use of the app store, and for the kinds of apps that are sold to the public, or other businesses, but are not publicly available, you have the definition of 'niche'.
Apple's management of the app store *may* kill iOS, but it wont be for the reason you stated above.
I'm surprised that during your evaluation process you'd missed this rather large detail.