Check out some of the sites devoted to Benchrest shooting. I doubt you will find many on here whom have experience with the NF Comp 15-55.
Although not a benchrest shooter myself, a few months back I picked one up. I reasoned that I would use the scope occasionally and it may be nice for group shooting and load development. However, I found that I rarely used it as I do not need that kind of magnification. I tested the scope in varying conditions prior to trading it for another Schmidt. The glass in the Competition is (at least to my eyes) far better than any I have ever seen in a NF scope. At one time I had 5 NF NXS's and I've had a couple ATACR's.
In my opinion the NXS is lacking in contrast. However, the ATACR has much better contrast and better glass all the way Rou d than the older NXS. I've heard that the ATACR and the Competition had the same glass and coatings. What I discovered during testing was that the Competiton seemed clearer than the ATACR and had slightly better resolution (both scopes set at 25x). If I were in the market for a high mag BR type scope, I would look no further than the Competition.