This year, both sets of 6-series 4K televisions include quantum dot LED technology -- also used recently in Samsung and Vizio TVs -- to improve their color performance even further, and the 55-inch version has a few more local dimming LED zones than before. This year, its new TVs also support using an upcoming iPQ Engine Mobile app on iOS or Android to help calibrate colors more accurately. It will only work with certified devices, like iPhones or Google's Pixel phones to get the levels measured correctly, and (ideally) allow users to adjust their TV with a level of precision that's usually not possible without specialized tools.
They also are some of TCL's first with "Auto Game Mode" that automatically detects when you're playing on a console or PC and need to use low-latency mode. That feature is part of the HDMI 2.1 spec but TCL didn't say if this is the same as ALLM. Their remote includes voice control, plus the TVs are compatible with both Alexa and Google Assistant.
A 75-inch 6-series with 2019's specs is supposed to arrive later this year, along with the higher-end 8-series TVs that use a new "mini-LED" backlighting setup with up to 25,000 individual lights. The 8-series TVs will cost $1,999 for a 65-inch, or $2,999 for the 75-inch.