I'm a big fan of the LG line this year. Though comparing it to the HX850, you get a lot of bonuses with that set. Both are going to be top notch image quality.
The Sony has incredible black levels, and shadow detail, which is important for darker scenes and movies. It also uses gorilla glass on the front, so it's a very tough screen, and easy to keep clean.
The LG is a piece of art. It's one of the very best television designs i've ever seen. It has extremely vibrant colors, and is a very very good all around performer.
If i had to chose, i'd pick the Sony for pure image quality, as my only tiny nitpick with the LG, is the light bleed is more noticable on a letterboxed image. If i was picking for my house (and keeping the wife happy) i would chose the LG. Either way, you won't go wrong.