4K LED will probably still suffer from Backlight bleeding/ bright blotches in dark scenes and blacks that are not Panasonic blacks, take care because both Sharp and LG LED suffer from backlight bleeding, i bet it's still there at 4K
what about 4K gaming on a big tv ? it'll be no good at all because Crysis 3 will look no better right now on 4K than 1080p, this is because the gaming world you walk through looks very poor and unrealistic compared to real life, it's not the resolution, it's the lack of realism, to get this right would require an Engine about 10 times more powerful than Cry 3 and a truly massive PC.
you will not see a truly realistic environment in a shooter, where everything is detailed accurately for at least another 10 years.... therefore 4K gaming on a large tv is a total waste of time.
yes, 4k will look sharper on a larger screen, but you are highly unlikely to have a 75'' screen at home, too flipping expensive and a bit too big for the average end of terrace LOL.
common sense tells you about 55'' to 70'' ( now that's HUGE) so this will be 1080p OLED.
The size limit of 1080P (REALLY IMPORTANT) i noticed was about 65'' but OLED is a much better image for its size than Plasma, so maybe this is about 70'', this is worth researching.
my 50'' Panny had a sharper image than my 55'', but i got used to the bigger screen quite quickly, but the image for the first 3 days deffo looked better on the smaller screen.