This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Well...I think its a difficult question to ask. Its like debating about Nikon or Canon both are great. So is the case with all the enterprise platforms you have mentioned. I have iphone and love apple technologies. I have recently started looking into android and it looks great too. One more thing you have missed is the new baby on the market called "windows phone 7" It is picking up slowly like how C# and ASP.NET did but I believe it will get a good market share too and stats predict that it will be in lead by around 2013 (based on the deal they have made with Nokia).
Anyhow, based on the criteria you have mentioned..this is what I think (my 2 cents)
- Development support (Apple iphone)
- Available API (Android as it is opensource and you can even boot your PC/laptop with some versions of Android available in market. Moreover dev platform is open)
- Applications in market (not a question at all....APPLE iphone)
- Easy to use (I think Apple is pretty easy to use for users..i have seen kids playing around with iphones, but same is for android too)
- UI design (iphone and android both are great. blackberry sucks)
- Future Enhancement (Android...as I already mentioned that its very flexible. You dont have to have an intel based Mac to develop apps like iphone
- Popularity (iphone)
- Target Users (Android is leading the market in target users as android is being shipped on various devices but that might change by 2013 as WP7 will be on nokia)