A:Answer Hi Jax, thank you for your inquiry. Both TV series is released in 2020. Both have HDR compatibility of HDR10, HLG, Dolby Vision, and supports Dynamic Contrast Enhancer, Object-based HDR remaster, and runs an Android OS. They only differ in the following:
BACKLIGHT DIMMING TYPE: The 900H - Local Dimming while the X800H - Frame Dimming.
MOTION ENHANCER (NATIVE HZ): The 900H - X-Motion Clarity, Auto mode while the 800H - Motionflow™ XR 240 (native 60 Hz)
PS5 Ready 4k/120/VRR/ALLM (with firmware update yet to be released) for X900H
You can also check the comparison chart for more details:
https://www.sony.com/electronics/tv/t/televisions?view=compare
Regards,
Erin