There are a vast number of differences between them but I'll give my own view on each:
Android is pretty much the best mobile OS there is, it's fast, flexible has great support for customisation, a pretty decent app store and it's becoming
Sergey Brin and Steve Horowitz discuss the availability of the SDK, that it will be open source in the future, and demo applications on the ...
What Does Microsoft Offer?
The workforce is becoming increasingly mobile. With so many businesses using Microsoft systems, workers need to access these systems from afar. Microsoft makes this possible with some key tools.
Microsoft Lync , an updated version of Office Communications Server, takes care of the communications needs. Lync provides group chat, Web conferencing, and software-based VoIP. Microsoft Sharepoint allows secure remote access to business data, which can be viewed and edited by Microsoft Office Mobile, the smartphone version of Microsoft’s cloud-based Office 365 collaboration suite. To prevent private business documents from being copied, edited, forwarded, or saved, the new Windows Phone 7.5 OS supports Information Rights Management (IRM) protection.
What About the Competition? Source: PCWorld (blog)
Daily Mobile takes a look at Illyriad on Android and iOS. Check it out here: 
The _Symbian_ operating system (OS) is utilized by many various mobile phone producers for their smartphones,... 
Motorola Defy is a full touchscreen mobile phone with Android operating system.
Illyriad: A Great Multi-Platform Game for Android Cell Phone Operating System and iOS: News from DailyMo... #Mobile
Android Development | Android ” Multitasking Mobile Phone Operating System 
droid pumpkin - carved while watching the yankees get blown out in game 1 of world series.
Giant Android robot at the Googleplex, Mountain View, California.