This is one of the biggest and more contentious TV tech questions of the moment. Luckily we've covered all of the details in our OLED vs QLED guide.
However, if you're looking for a summary we'd say that QLED is a great option for brightness if you'll watch in bright, sunlit conditions; whereas OLED TVs offer better viewing angles and superior contrast for gorgeous movie-like images, as long as you can control the lighting.