As many have stated, I like Android for its customization and freedom it provides. In particular the ability to root and make system modifications if you wish. Also, as an IT Pro (17+ years now) it's the most intuitive to me compared to any other mobile OS.
My biggest dislike is there isn't a native way to control Android OS updates without rooting your device and killing the OTA updater. IMHO, Google needs to build that into the OS like Microsoft does with Windows so users have more control over the update process. As it is now, without root and killing the updater, you're at the mercy of Google, the OEM, or your carrier. Your device may get updated in the middle of the night (or worse; a time when you need to use it) whether you wanted it to or not. Many times that results in the user spending an inordinate amount of unplanned time troubleshooting and trying to fix a problem the update introduced to what was otherwise previously a problem free working device.
Another one is the way Google automatically pushes out updates to Google Play Services behind the scenes without the user's knowledge as if it's their device and they can make any change to it anytime they wish. This is the type of behavior Microsoft got into big trouble with in the past with Windows Update.