The display measurement experts at DisplayMate posted a very interesting article comparing LG's 65" 4K OLED TV (the 65EG9600, which costs $5,999) and Samsung's top of the line 65" 4K LCD (the UN65JS9500). DisplayMate performed dozens of tests, comparing those two high end TVs in several scenarios.
DisplayMate finds that the OLED TV outperforms the LCD in all the tests - the only category in which the LCD outperformed the OLED was brightness with average picture level higher than 25%. Specifically the OLED offers a higher contrast, a higher color accuracy, much better viewing angles, faster response time and higher power efficiency.
DisplayMate says that this is the best TV they ever tested - and it actually outperforms Sony's professional CRT monitors - that cost $50,000 and are regarded as the golden standard for picture quality.
Samsung's LCD actually performed exceptionally well - for an LCD display. The TV features full-array local dimming, quantum dots, and a curved screen - but a major disadvantage is the poor viewing angles - viewing the TV in any position other than the sweet spot decreases the picture quality noticeably.