In my opinion:
Windows Phone has some nice device-specific features but no apps. I could see people who care more about just the phone itself vs. apps appealing to this. They also need to get more apps in the store instead of having like 13 knock-off Gmail apps.
Android a spectrum in the middle. You can feel the compatibility issues when using apps. You get the freedom of choice in the diversity of devices, but the apps are mediocre (like Michael Crabtree).
iOS is still superior in apps—both in terms of performance and what is out there. iOS 7.1 performance is even faster.
FYI: I have devices with all three operating systems.