One of the advantages of QDs is that they emit "purer" R G or B than current LCD solutions. Purer colours appear brighter - and that's on top of the far lower loss through the panel because white light isn't being filtered down to a single colour then those colours recombined in the eye (A "white" screen is usually less than half the brightness of the backlight behind it.)
One of the disadvantages is that no two people perceive R G B in quite the same way, with the response curve for each colour in the eye being slightly different from person to person.
This means that perfect colour space representation for one person can seem "off" for someone else and tetramats are likely to get headaches.
As for OLEDS, there's a simple reason they're not being sold in the larger sizes - yields are too low - where the same area of a screen with a couple of defects that would get written off for a single TV would make a dozen phone screens with no defects at all. This is the same chicken-egg problem that existed to keep large scale LCDs off the mass market until production quality was nailed and then we had a flood of the things.