I used to have one (sold my ST-10 to get it) and I can tell you that of all the scopes I have owned, the 10x42 S&B had the best glass quality. The image through that scope was flawless, bright and almost 3D like. It was even better than 34mm S&Bs I have. I feel that the S&B is the bext fixed 10x out there by a wide margin.
With that being said, I would still prefer a variable Nightforce if it were my only scope.
I have two S&B 10x42 PII. One is the older version. Fixed means less glass to look through. Parallax is not a issue for the S&B. In my eyes there is no comparison. The NXS is a good scope, but different? Buy and try it. The S&B go for 1200 used. You will never really know until you get one and try it.