My personal review of Hisense 65u8h (vidaa version) after using it for 1 month+
1) vidaa os is very fast. of course feature wise it loses out to google/android os but the speed of loading up and switching screens is a positive. If you use Samsung phones like me, you can use Smartview to simply cast your phone direct to the TV (don't even care about no chromecast support at this point lol). I can also stream videos direct from my PC through content sharing mode (with subtitles on and everything).
2) bright scenes hisense wins hands down, the lg demo where the 2 parachuters face each other in bright daylight looks so realistic, I thought I was there with them.
3) black scenes are also very impressive. It is not oled perfect and in very contrasting hdr scenes you can see very slight blooming, but for the average viewer it is really not noticable. Also, certain black scenes you can see black levels being crushed - so that's a negative there. I have also observed occasionally certain HDR modes will jerk for a split second or so. I can't confirm what it is due to but I read online it's likely due to hisense cpu not being exactly that strong.
4) recommended settings to use - cinema night/filmmaker mode in SDR mode and HDR night/filmmaker modes for HDR (use warm2 or standard temperature). Turn off light sensor mode and lower backlight level to below 50 (mine is set to 25) or if you like it on (I find it too dim for most scenes), add +10 to auto backlight level. Also change color gamut to Auto instead of Native in SDR mode - you will wonder why you didn't do it sooner.
5) Turn off all smart scene/adaptive contrast/noise reduction/etc settings if you prefer a purer picture. For Ultra Smoothing, I also turn it off but for certain jerky scenes, turning it on is actually better. The soapy screen effect trade off is pretty much minimal for these cases.
6) I use hisense h219 soundbar and if you don't have a 5.1 setup, change the sound mode to passthrough or PCM instead of Auto, or else the sound will be too soft.