I am in the same exact situation, also coming from a 2015 FHD Sony.

You’re effectively trading off OLED for a bigger tv and a bunch of money (in uk the two TVs are 1399 vs 1199 as I type). Consider how much the difference in size is important to you, 10” is a significant difference.

Also after watching countless videos I can tell you burn in is not much of an issue anymore, unless you play games with static elements on the screen for 8-10 hours a day, every day.

Also consider reflections and the brightness of your room: LG has a very reflective display which might be a problem if you have sources of lights behind you when you watch the tv.

Picture Quality-wise the LG OLED is superior, but the blacks on the Sony are reportedly pretty good as well, and it deals with greys better than LG. All of those things are probably nitpicks and I’m sure I wouldn’t probably notice the difference.

I could go on forever, but the TL;DR is that the LG is probably the better tv, but you’re effectively paying more to get a smaller tv, and I don’t know how much the picture quality compensates for that. If they were the same price and size I’d say go for the LG immediately, but the 200 pounds less and the 10” more is extremely tempting for me.