Bravia KDL46-NX810 vs Samsung UN46C8000XF

I just bought a 60NX810 a few months ago and my uncle has a 46NX810. IMHO, the Sony has more natural color and the Samsung looks a bit cartoonish. But the screen of the Sony is a lot darker and may not work well in a bright room.

I don't have the model you mentioned but do have the Sony Bravia KDL 46V5100. The deciding factor for me was when the salesman demoed them side by side. In that situation the Sony was clearly the better set. The colors are more natural and revealing. The Samsung has more of a blue tint which when viewed by itself gives the impression/illusion of a more dynamic picture.
I to have a large room with high ceilings, lots of windows and white walls, in that enviorment LCD or LED is the only way to go, Plasma will not work.
My two cents.

Unfortunately, I don't know a shop where I can demo them side by side in my area. In fact, my only option is the well worn big box electronics store (you know the one!). There, all brands looked far brighter than the Sony, and I'm leaning toward the Sony. Did you folks have your sets calibrated?

It's tough to beat the Sony. (we sell them) That being said, after years of having all Sony in my house, I've switched. Sony does not offer a plasma anymore, and IMO, the LCD's, and LED's are just not as good a picture. You can have issues with gaming however. (if thats important to you) Everyone has an opinion of their own, thats just mine.
All of my friends, and family are using plasmas, FWIW. I have a 60" plasma in my living room that faces the East. Light has never been an issue for me, and I have windows that overlook the water, so I get lots of light.