Here are two infographics which compare the 4 smart phone operating systems.
iPhone iOS Vs Android Vs Blackberry Os Windows Phone 7.
1. iPhone iOS 4.3.3 Vs Android 2.3.4 Vs Blackberry Os 6 Windows Phone 7 (Click below Image)
2. iPhone iOS 5.0 Vs Android 4.0 Ice Cream Sandwich Vs Blackberry Os 7 Windows Phone 7.5 Mango (Click below Image)
[Via CNET]