It depends on what model are you comparing, because there are some good QLED Samsung’s, and some good Sony... but also some bad ones.
If you’re looking at Samsung, the Q70R and up are the only models that are great. They have full array local dimming, and a nice wide color gamut and volume. The Q80R and above have an optical layer that gives you a wider viewing area. The only thing I don’t like is that they are hell bent on not supporting Dolby Vision.
Sony has a great LED and even a more phenomenal OLED. Their picture processing power is great, and while they don’t market QLED their X900F and above models are very similar but slightly made different. Sony has a better overall performance but the Samsung Q80R and Q90R are better with color volume and black level performance.
I still think OLED is the way to go, and gives the best picture hands down.