It also doesn't mirror over from the streaming device, it just loads the content to Chromecast. Therefor causing your devices battery to save power and stop the lag that you get when streaming to Apple TV.
I think there may be som misunderstanding here. First of all AirPlay can be divided in three modes:
- AirAudio for pure audio transmission. Typically used by music players. Apps making use of this can be run in the background while you use something else in the foreground or turn your display off.
- AirVideo for video (with audio) transmission. Typically used by apps like NetFlix, HBO and some video players. Apps making use of this can usually be run in the background (exceptions may exist) while you use something else in the foreground or turn your display off.
Last time I checked, AirVideoing for 1.5h with the display off consumed something like 1% or less battery on my iPad, so it is not such huge battery hog as some people claim, at least not from my unscientific experience and neither have I experienced any lag or choppiness.
- AirMirroring where the whole desktop is mirrored. Convenient for apps playing music, videos or pictures with no AirVideo support or if the format they play is not supported by iOS. The apps playing must be in the foreground and the display must be turned on. This mode (which I think you were thinking off) drains the battery a bit more and can show a bit of lag and/or choppiness (not too bad thought).
If you use a MAC and install a Safari extension called ClickToPlgugin, you can send youtube links directly from your computer to ATV. Once done the computer can be turned off (may work for other services as well, but I'm not sure).
The beauty with ATV is that you can pretty much send anything to it from any iOS device (not sure this is the case with ChromeCast).
From what I'm seeing Chromecast supports native HBO Go, Netflix, Youtube, Hulu Plus, and Pandora now.
As mentioned previously, most of these services support AirVideo as well when run from an iOS device. However, they are also natively supported by ATV so you don't need to run them from an iOS device.
Apple also provides an iOS remote for ATV, which makes navigation much easier.