The reason Samsung isn't making OLED panels isn't because they think their QLED tech is better, it's because LG bought the patents for the tech and Samsung would have to pay LG to manufacture them.
OLED is simply the technology of the future. At this point in time the OLED TV's are better in terms of pure image quality. If you're buying a high'ish end TV for the absolute best picture quality, the LG or Sony OLED panels are the way to go.
Sony A series OLED has better image processing and color banding gradiation due to their superior image processor technology. The X900F LED TV series also has a similar graphics engine and is absolutely great if you want a low priced LED LCD TV.
The difference between LED/LCD and OLED is lighting. LED TV's still utilize an LCD substrate with lighting behind them. You can't get as dark that way but you can get MUCH MUCH brighter. That's important if you are putting the TV in a very bright room. Even a moderately bright room can be tough for last year's models of OLED TV's. Just like plasma TV's of old, you simply can't get the brightness from an emissive picture source, one where the actual pixel emits the light, like Plasma or OLED.
A permissive tech like LED backlit LCD, will never get as dark as a permissive tech because you can't turn the light to 0. For most people the difference in tech won't make a huge difference.
Now the real personal preference here is with HDR content, which is high dynamic range, or for simple understanding more colors and a larger contrast between dark and bright things. If you like really eye popping bright colors the Samsung sets have always been very good at being able to blast over saturated colors with tons of brightness at you. Many people really like this and it makes for a pleasing experience.
Others like true to source material (showing colors in exactly the way film and show creators mastered them) and others like very natural colors or some combination of both. It's difficult to reproduce things as the eye sees them with over saturated brightness and OLED can handle a very wide color gamut accurately without using extremely high levels of brightness, which it has to do since it simply can't reach those same levels of brightness that LED LCD can.
QLED is just a new filter on old tech. Standard TV's would have a filter layer in the LCD sandwich. This would be usually two different sets of filters for polarizing then the latter filter for allowing/shutting off light. Quantum Dot isn't really quantum at all, it's changing those from static filters to a membrane filter that can be electrically manipulated to allow the LCD crystalline substrate layer to have the best performance for color and brightness. This is the pinnacle of LCD technology today.