I have the xbr850c and I just got the ks8000 this week. I was expecting the ks8000 to blow the 850 out of the water, when it came to HDr. Using the Revenant on a Samsung UHD player. I would say the difference is minnimal. Yes the Samsung is brighter. But not to the point of making the picture better. The HDr highlights mainly fire in this movie pop on both tv sets.
Actually because in my current setup the Sony handles color, contrast and motion better then the Samsung, you actually see more detail on the 850. The Samsung over saturates color so much that on bright scenes it will look more vibrate, but the Sony will actually process more shades of the individual colors.
I have only had the Samsung for a couple of days and can probably adjust it to more of my liking via calibration.
I don't have the Xbox one s so I can't test games on either tv. But when it comes to HDR on the Revenant at least the difference between 282 nits verse a min of 542 on the Samsung does not make much difference.
I had the x850D at the moment, becasue of the insanely high input lag, I am planning to take it back to the store this weekend and wait until black friday. Was going to swtich it with the ks8000, but the demo they had running at the store did not impress me at all. They actually showing HDR video of Alberta where Im at which was a nice touch. However the picture was super grainly and overly sharpen. Remind me of my old Samsung that would not allow me to turn off its edge enchancer no matter what. Motion is defintely one huge advantage the X850D has over my last LG so, picture and detail stays razer sharp in fast motion which is very important for game only for a small sacrifice in brightness. If only sony would come forward and officially state that they can decrease the input lag of the x850D down to the same level as 1080p game mode via the upcoming Android 6 update, I am not going to risk this 1500+ investment.