I have a couple NF NXS scopes, an ATACR, and a S&B PMii. I will agree with the others that NXS glass is ok, but not "great". The scopes are very robust and track perfectly, so durability in the field shouldn't ever be an issue. They are a little heavier, but that's the tradeoff for extreme durability. The rotating eye piece does cause a problem with flip covers at times. However, I do like being able to grab the entire eye piece and rotate to zoom. It's very easy to do when wearing gloves. I've gone to using neoprene scope covers instead of flip caps on my NF scopes. I can get the cover off just as fast as opening the flip caps. The neoprene cover also provides some additional protection to the scope that flip caps do not. It can also be used an a make shift rear bag when shooting prone.
I've never looked through a VX-6, so can't comment or compare. ATACR glass is a little more clear than NXS to my eyes. Neither are close to my S&B, but honestly, unless you are reading print at 100 yds +, I'm not sure it matters on a hunting rifle. The NXS glass is perfectly adequate for the use, and is not a hindrance in any way.
Reticle illumination is a bit quirky on the NXS, and the parallax and windage knobs stick out to the sides quite a bit, so it's easy to snag them on clothing or other things when carrying the rifle. Overall, I'm very happy with my NXS scopes. I prefer the durability and solid tracking to something that will save a few ounces but might be out of commission if I take a tumble in the back country. I can work around the flip cap issue with a neoprene cover, and although the glass is not as good as some other options, it is perfectly usable.