I went through this last month with these exact sets. I ended up with the Samsung 65KS9000, but it was a very close call.
I see these other comments on waiting for something better, but the problem I have is if you follow this philosophy, there is always something a bit better on the horizon. One either ends up with analysis paralysis, or end up with the set of the month and upgrade several times a year. ($$$)
My philosophy is to look at the emerging standards and wait until the technology stabilizes. Then upgrade and stop looking until the need arises. The reason for me was a bedroom TV that failed and a 50" Panny plasma that was showing its age. I moved the Panny to the bedroom and the new Samsung into the family room.
OK, now the comparisons. Forget all they hype about proprietary technology. The key is in what you see, especially what you will see in a properly calibrated set. You are not going to be able to tell much in the torch mode they show at the stores. Try to find a sympathetic salesperson and let them know you are willing to buy, but need to see what you are getting. You aren't going to be able to do a full calibration, but you can use the picture mode settings to get you close enough to evaluate. Try to set the TV to "cinema" or "THX" mode. Double check the video settings to make sure contrast is set down, color temperature is at 65k, sharpness is set down, edge enhancement is off, etc. Only then, start comparing pictures. Hopefully you can use the same source for each.
When I did this, I found that the Sony and the Samsung were so close that it was impossible to choose between them. It really was a coin flip for me. I ended up choosing Samsung mostly because of the fact that I have had reliability issues with Sony XBR in the past. The Samsung was initially $100 higher, but it went on sale the next week, and I got a $200 refund.
I went in loving the blacks on the LG and being very impressed. I was ready to go with it. However, after adjusting the picture, the difference wasn't nearly as striking. Mind you, I still preferred the picture, but I simply couldn't justify the extra couple thousand I needed to get the same video processing on the LG. The lower end LG OLED sets really are more comparable to the Samsung 6000 or 8000 series in terms of HDR, quantum dot and basic upconversion. I could see the artifacts, and needed to go to the higher priced model if I wanted the OLED.
BTW, don't even think about the built in audio. You can't believe the junk sound they put into a $2500 TV these days. Its never been good, but the sound was horrible on all the sets I auditioned. Doesn't matter to me, as it all gets fed into a 7.1 system with classic Klipsch speakers, but if you don't have a dedicated HT setup, plan on budgeting at least for a good soundbar.
I have now had the Samsung up on the wall for 3 weeks, and have watched 4k from Netflix and 1080p broadcast and BluRay. I see a more noticeable difference on broadcast between OTA and TWC than I did with the plasma. It is actually striking. I expect to upgrade to UHD player soon, but I am waiting for the Oppo.
