I stood in the store for a long time looking at both the Xbox One S and the Samsung UBD-K8500 4k player. I'm not a huge gamer or anything, occasionally pop one in if I feel like killing an hour or two doing something mindless... but in the end went with the Xbox just to have that capability. I was replacing an old PS3, and did like the added feature of it being a gaming console if I got the itch to play games and figured if it plays 4K discs as well as the old PS3 played regular Blu-rays it's a no-brainer. However I was rather unpleasantly surprised when I got it home and got it all hooked up and running to learn that it did not support anything more than standard Dolby Digital and DTS formats..
I hadn't bothered to research this part (my own failing), incorrectly assuming that if the thing played 4k discs it ought to damn well play the advanced surround sound formats, but boy was I wrong. I can't comprehend why Microsoft made such a glaring omission in this regard and keep seeing indications that a firmware update will come out this year that will enable those formats, but until it actually happens... even the old PS3 (the original fat boy mind you, not the slimmer version they later came out with) support True HD and Master formats. It made no sense that the Xbox One S didn't even do those for crying out loud. So I currently have mine set to 5.1 uncompressed audio out to my AVR, and though its arguable whether or not a PCM or bitstream output in those higher formats would yield significant improvements to the sound, I still like seeing the indicator on my AVR showing that it's playing the highest format available on the disc.
Thanks a lot Microsoft.... lol