[lxgr]

One important difference is that Airplay is much more of a screen or video mirroring protocol, while Google Cast is focused on the receiver driving presentation, with your mobile device only acting as a navigation source.

Practically, this means that you can take phone calls, hibernate your computer, kill a source app on your phone, leave the house entirely etc. with Chromecast without interrupting whatever's playing on a TV or stereo, while with Airplay, playback usually stops in these scenarios. Airplay is also a bigger battery drain as a result, in my experience.