Operating Systems/iOS vs Android

If we've learned anything in our years of mobile app development, it's that many smartphone and tablet owners are very loyal to one operating system or another. Whether it's Apple's iOS or Google's Android, we know folks who can give you a list as long as your arm why one is fantastic—and the other, not so much. Everyone has in their mind what's important to them in a mobile device, and they usually find one operating system fills the bill better than another for them. Millions of passionate words have been committed online to this topic, so we figured: why not a few more?
We invite our Appvice Community members to use this thread to extoll the virtues of their favorite operating system—and to nicely make their case against one they may not care for. Also, if there's an operating system besides iOS and Android you feel should get more attention, let folks know here. Vigorous debate is fine, but please respect the opinions of your fellow members—and that they may not align perfectly with yours.