I've looked at this a few times, and AppleTV actually has pretty poor support unless you're only using a select few streaming services and not streaming any of your own content. Shield performs exponentially better in every way except for the god awful stock interface (and Google data collection vs Apple data collection). The hardware and tvOS still have extremely limited support for most video codecs, no support at all for audio pass thru, and very limited non-stereo audio options. If you want the equivalent of watching on your laptop it's good, but if you have better than stereo speakers, or a 4K TV that supports HDR10+ or Dolby Vision, AppleTV can't compete except for the big name streaming services that have special tvOS privileges/integration.

What makes the Apple TV desirable? It’s $185. Why would I choose it over a Roku $30 or Ultra $80?