Well it has different viewing options ("more open" for whatever that's worth). Based on Google's own promotions for Chromecast you gain Google Play and Pandora, and lose iTunes. There's a bunch of other tradeoffs I'm sure (I assume, for example, there's a PBS app for Chromecast just as there is for AppleTV. AppleTV supports Amazon video via AirPlay -- which is good but not great; but Amazon video simply won't play on Chromecast.)
Chromecast is more intelligently architected than AppleTV (you hand off to Chromecast rather than remote-controlling it) but I suspect AppleTV will address this shortly. OTOH AppleTV works with any remote, and you can use any iOS device as a remote, and AirPlay is wonderful.
Chromecast is more intelligently architected than AppleTV (you hand off to Chromecast rather than remote-controlling it) but I suspect AppleTV will address this shortly. OTOH AppleTV works with any remote, and you can use any iOS device as a remote, and AirPlay is wonderful.