A:Answer X810C is a 2015 4K SDR carryover model that can only receive but not display HDR . X850D is 2016 HDR wide color gamut and Triluminous back lighting ,the X850D would be worth the extra money IMO . OTOH X810C is a real decent 4K SDR TV but the equivalent 2016 Samsung's and X850D can get much brighter .
I have the 2015 55X850C with the Triluminous wide color Gamut backight panel like the X850D it can make better primary reds ,greens ,blues and and 1.2 Billion colors vs maybe 1.7 Million on the X810C .Keep in mind we can see 14 bit color that has many,many more colors than any TV you can buy today . The best consumer TV's now can reach ~1200- 1800 NIT (cd/m2) of brightness (luminance ) in small window , an average noon sunlit day is 11,000 NITS . These 3 TV's are well below 1200 NIT ☺
All these sets have 10 bit panels but the X810C lacks 10 bit processing and the wide color Gamut Triluminous panel light spectrum .
I looked at the X810C before I bought my X850C and it was readily apparent the Triluminous HDR X850C was the better TV I would expect the X850D would be also.
The X850D replaced the 2015 X850C which is actually the best of all three of these .
