Sony has been making OLED screens and viewfinders for years now, so they've had the technology long before LG was in the business. Strange that they wouldn't apply it to their TVs if they thought it would make for a better product. Maybe there's something they about it they don't agree with.
Sony is still marketing its non-OLED Z9 as its flagship, as it is uniquely endowed with Backlight Master Drive. The new Sony Bravia OLED has the same X1 Extreme Processor, but does not have the Backlight Master Drive, and it uses an LG Display panel. While I'm not an expert on the specifics, I believe that OLEDs either aren't compatible with the Master Drive, or don't need them due to the way they create their own light. In any event, Sony is saying that its OLED model has superior black levels, but the Z9 has superior brightness.
LEDs won the LED/Plasma fight in part based on their superior brightness, and in spite of their inferior black levels. In my opinion, based on seeing the various offerings on display at CES, OLEDs are bright enough, and black levels win the day when it comes to color and overall picture quality. That being said, Samsung is doing a great job with its Quantum Dot tech, and despite the ridiculous QLED name they dreamed up this year, their TVs look very good. I personally use a 2014 Samsung 4K TV, which was the best at the time, but if I were in the market for a new model, I'd either go with LG's OLED or a Samsung Quantum Dot.