Aside from excellent color on OLED tvs, in a brightly light room (sunlit), you can’t really tell. However, in a dark room you’d have to be blind not to instantly notice how much better OLED looks due to the inky blacks which makes the colors pop. A properly calibrated LED tv is still going to look washed out in comparison. Even my neophyte wife thinks our theater OLED tv looks a lot better than our daily use LED tv and they’re in different areas of the house.

Saying that, I would never buy current OLED tvs for a brightly lit room as they aren’t bright enough to overcome the sun. That’s where LED tvs shine (pun intended).