Apps - 5
Camera -4
UI Customization -2
Games -5
Battery Life -3
Custom ROMs -2
E-Mail integration -1
Social integration -1
Multitasking -3.5
Alrighty. I'll answer them one by one.
Apps - While there are loads of apps on Windows Phone and I am content with the apps available (I'm using all free apps since I've kept a US account for the sake of podcasts) but developers don't exactly feel this way. Any new snazzy app will be released on iOS and Android first. So there might be some specific apps that you will not find on Windows Phone. But the plus point here is that most apps will not crash or behave in an unexpected manner. Even the ones which have a very bland UI (referring to inexperienced developers) don't crash at all. Android gives too much of a free rein so there are lot of unstable apps there. Also, the apps which utilize the Metro UI (a very good example is the
IMDB app and the
Prime TV app ) are really, really beautiful with slick interfaces.
UI Customization - Windows Phone suits your need since the only customization you can do is change colors.Which is not a bad thing.
Games - Again, similar to apps, some games do not make it to Windows Phone. And the good ones that do, are paid and expensive. So, Android does have kind of an upper hand here.
Battery Life - My HD7 with constant email sync for 5 accounts and light 2G usage lasts me 24 hours. With 2G off, it lasts nearly 2 days. Omnia W has an even better battery life. My friend's Omnia W lasts 1.5-2 days with email sync enabled. Better than Android
Custom ROMs - Options very, very limited for Windows Phone 7 as you would expect. Not at all needed here since performance is superb but it's not there.
E-Mail integration - Linked inboxes in Windows Phone 7 are awesome. All mails in one screen with threaded conversations in glorious Metro UI. Really seamless.
Social integration - Excellent in Windows Phone 7. Post and check updates for all social networks simultaneously. Though FB contacts are present in Android phone too, the presence of FB chat integrated into Messages so that they exist alongside SMS messages is too good. I've started using FB chat a lot now. The chat comes as text messages and maintains threaded conversation view.
Multitasking - Implemented as App freeze, not true multitasking. 5 recent apps are frozen. Works really good with native Windows apps, but 3rd party apps are a hit and miss. But, the positive side of this is that apps never take over your phone. The performance of the phone never drops. I prefer it this way rather than always looking over the Task Manager and switching off apps. Again, it's a personal preference.
Phew, so there I've mentioned the points according to my time spent with Android (1.5 years) and Windows Phone 7 (10 months). Feel free to ask if I missed anything.