Next time you create a poll think about it, it's:
Android vs iOS vs BlackBerryOS(RIM-OS) vs Windows Mobile
Android: I love freedom, this OS gives you freedom of the os, fully moddable and great growing marketplace, and ofcourse it's OpenSource! Technically great system and mobile kernel based on Linux.
iOS: Powerfull operation system, very very stable and fast. Totally NO freedom if you didn't jailbreak your device. Easy to develop software for it.
BlackBerryOS: Very fast, very hard to develop software for this OS, java based OS. Easy to use powerfull radio software (This is not normal radio:P, this radio software controls GPS/Battery/3G).
Windows Mobile: Lost a big part in the MobileOS world, I personally never checked Windows Phone 7 software but the old WM6 was okay, nothing more. Not really stable.
My vote goes to Android.
@Djlatino, Bill Gates has nothing to do with the development of windows, neither Windows Mobile/Phone. Bill Gates is busy counting his money.