Posted this on a gaming forum, I'm more on the gaming side...
I have the LG 49UB850 for almost two months now, so far gaming has been great. Wala naman masyadong lag. mas recommended ko siya sa PS4, kasi most games are 1080p, so times four more squares kahit na upscaled malinis pa din tignan dahil higher density ang pixels. Imagine retina display only on a tv. TVs. As for ps3 games di ko masyado ma recommend ang 4k, upscaling makes the graphics look too soft. pag hinabol mo naman sa sharpness, magkakaroon naman ng white outline. Hindi naman sa lahat though, mas mapapasin mo siya sa mga games na sub 720. Mas marami kasi siyang hahabulin na pixels.
Sa movies naman, same lang with 1080 TVs, may difference lang talaga pag pang 4k ang video mo. Mas recommended ko pa din ang 1080p movies on 1080p televisions, native kasi ang resolution kaya mas sharper pa din. Pero may enhancers naman ang 4Ktvs to compensate for lower resolution movies.