[wrxtasy]

So ATV4K: no atmos, no passthrough, no 4K YouTube

The Apple TV 4K does lossy Atmos audio when using copy protected video streaming Apps like iTunes, Netlix and VUDU.

It cannot do Bluray Rips Atmos Audio passthrough.

Also to add is the Shield does below average 1080p > 4K picture upscaling. Kodi Leia has a workaround for that within 1080p / 4K resolution switching, but other Apps miss out.
The Shield also has no Dolby audio license to support older DD only equipment and no DolbyVision support if you have a 4K DV TV and Apps that support that type of HDR.

There are other limitations .....

Read the linked sticky threads at the top of the forum, there is already plenty of information already written about various platforms limitation and ongoing problems.