Game emulators
It nice to have the games, physical remote, Kodi and the ability to sideload apps directly on the device while still having googlecast.
I love my Chromecast and use it every day in my office. But in the front/living room it is nice to have the menu options so everybody can collectively browse the options to watch. Its very wife/family friendly.
If you have an older TV that does not send commands through HDMI it will let you pause what you're casting with the remote.
Only after using my Chromecast on a friend's new Ultra HDTV did I realize the Chromecast will let you do the same thing giving you're using it on a newer television.
Like others have said, if you have any other people using it, I consider a remote basically essential. I would rather just give me wife the remote and have her look at things to watch instead of having them cast things from their phone/tablet. Especially with trying to pause/resume things, unless you have HDMI CEC working, it is just so much easier with a remote.
I use a shield TV and a harmony smart control remote.
Honestly as of right now, not a lot. There is practically no apps for Android TV. A lot of functionality depends on Chromecasting.
A superior UX. Which doesn't sound like much, but it's so intuitive and slick that if you do have non tech people using it, they will fall in love as well.
I had the original Chromecast, and I just purchased a Nexus player.
It's nice to have an actual menu.
its nice to have a dedicated remote
The voice search is pretty damn good.
you can re route the audio to Bluetooth headphones
you can play games on it with a Bluetooth game pad
I find sometimes my phone randomly disconnects from the Chromecast, so the only way to stop whats playing is to turn the TV off. This doesn't happen because the remote is always connected.