The comparison of the two TVs above is not representative for all NanoCell or QLED TVs, but it gives a good overview.
Basically, it can be said that NanoCell TVs are better for bright rooms because they have an IPSIn-Plane Switching, type of LCD Panel panel. Thus, they have a higher brightness, can handle reflections better and have a wider viewing angle. Unfortunately, their black level is rather weak and has a slight gray cast.
QLED TVs can match the peak brightness of NanoCell TVs, but they use VAVertical Alignment, type of LCD Panel panels. This means a narrower viewing angle, but much better and deeper blacks. The contrast ratio of VA panels is also much higher. This makes them better suited for very dark rooms with few light sources. The more expensive QLEDs in Samsung’s lineup starting with the Q80A mostly use an IPS panel, which is why you should take a closer look here since some sizes still use a VA panel. Furthermore, the Neo QLEDs offer a mini LED backlight, which increases the contrast ratio even more. This is especially noticeable in the top model QN95A with its VA panel.