Only a few differences despite new display technology
Samsung does not advertise with the new Mini LED technology for nothing, because the QN85A and the Q80T only differ slightly otherwise. The biggest difference is probably the panel, which is completely different on both TVs. The IPSIn-Plane Switching, type of LCD Panel panel allows for a significantly higher peak brightness, but the VAVertical Alignment, type of LCD Panel panel from the Q80T performs much better in terms of contrast and black level. However, it can really shine in bright rooms as it handles reflections well.
When it comes to gaming, both devices are a pleasure to use, as they hardly differ from each other in this respect. Both have an HDMI 2.1 port, which makes 4K@120fps possible, and the motion handling is also convincing. The QN85A also has Full Array Local Dimming enabled in Game mode, which means you get good picture quality even when gaming. In terms of sound, both TVs have to do without DTSMulti-channel-sound-system (Surround Sound) competing with Dolby Digital and the bass is rather poor on both. However, this can be easily remedied by connecting a soundbar.
In the end, the QN85A emerges as the winner in the comparison, even if you still get a very good mid-range TV in your living room with the Q80T. Especially users who like to watch during the day or in a very well-lit room will have fun with the Neo QLED. However, if you like to watch movies and series on your TV, the Q80T performs much better because it simply displays contrasts better and thus delivers a better picture.