How are these devices connected to the system? Direct to TV or to receiver? It matters in a few ways. I use the Apple TV 4K after having tried a Shield Pro, Roku Ultra and XBOX Series S. It was the best all around solution in my case.
The XBOX requires the download of the Dolby Access app for Dolby Atmos playback and “Dolby Atmos for home theater(HDMI only)” needs to be selected for output. It will upmix all content if passthrough of content is not also selected. This, however, applies to video content, not games. The XBOX can also convert ALL audio to DTS:X with the download and selection of the DTS app.
The Apple TV converts everything to PCM and only Dolby Atmos tracks will trigger the Dolby indicator as it uses Dolby MAT to deliver the audio. This will not work when connected directly to a TV that supports ARC as the bandwidth is limited and a direct connection to the receiver is necessary unless the TV and receiver both support eARC.