I have owned many LED tv's over the years and several OLED tv's. OLED gives far better picture quality than LED/QLED. You only have to look on the countless review sites or AV forums to see this to be the case. QLED still suffers from the many issues LED suffers, which in my situations makes the picture quality worse. OLED isn't perfect either. However, its a lot better than LED and as the technology matures it will keep getting better.
I also agree with previous posts that QLED is basically a marketing term and whether intentional or not, can be confusing for customers. Its like when DVD HD players were released before the official HD DVD and Blu Ray players. The DVD HD players were a marketing term so people thought they were getting true HD picture quality, which was confusing for customers. But in fact they were just getting upscaled DVD picture quality from these players and then needed to buy a second device to play true HD DVD or Blu Ray.
As for the recommendations on buying a 3D 1080p tv over 2D OLED, I think this would be a mistake unless your heavily invested in 3D. If you don't own 3D or don't own many, I would seriously consider getting a 4K HDR tv. This could be either LED or OLED, depending on what you can afford. But to buy a 1080p 3D tv now if you don't require the 3D component would be ridiculous. 3D is a dying, could be said dead, format. Many major manufacturers are not supporting 3D in their tv's anymore and 4K Blu Ray's aren't supporting 3D either. There are countless articles on many websites confirming this which can be read. You will be able to continue buying 3D movies for years to come most likely. But as more tv's, players, etc get released not supporting the format it will slowly disappear at some point in the near future.
So if one can afford it, I believe an OLED tv to be the better choice. This is not to say you shouldn't buy an LED tv however.