The remote and navigation of the sony is poor to put it lightly with gazillion buttons that you hardly use. PQ has been very good compared to LG but we are comparing apples and oranges here. LG remote and navigation has been not an issue.
It has been a general problem to move the movie timeline slider to exactly where you want in both the tvs. This issue looks like been efficiently solved in the apple tv using the jog wheel. Another issue is general usability of voice commands especially in sony.
I cannot discern any difference between the PQ from the apps on my Sony and the PQ on the ATV 4k; then again, I do not have a keen eye. I'm perfectly happy with the PQ on both.
The sole reason I acquired an ATV 4k was for the clean UI and the terrific remote (latest version). Once you get used to the jog wheel there's no going back. The UI is slick, and in conjunction with the jog wheel, which is also a touch pad, browsing is snappy. The voice input on the remote to search for titles is quick and works as expected.
In comparison, Android TV is clunky, and stutters (occassionaly, it's annoying to me nonetheless) ) on my TV. I'm not sure if Android TV isn't smooth enough or the TV processor isn't able to keep up with the UI.