XR50 = Bravia 5- is a spiritual successor(?) of the highly rated Sony X90L series. Sadly it is downgraded and didn't perform as well as predecessors. Sony continues to rely on its excellent picture processing continue to carry its mid-range - upper mid models.

QNED92 = A new gen of LG MINI-LED that is using TCL VA panels instead of the usual IPS . Result is drastically improved contrast and higher peak brightness. But LG has sub-par local dimming compare to others , despite packing better hardware than similar TV models.



TL;DR
XR50 has less impressive hardware but the software side ( upscaling , motion , local dimming etc etc ) makes up for it.
QNED92 has better hardware but the local dimming performance is subpar.


In general they are likely in the same performance bracket.
Whichever you should buy will depend on which you get a better deal out of.

Personally I would gamble on Sony's. LG's LCD remains in the niche category. And yes that is after considering that they have replaced some of their LCD with VA panels.