There are like in everything else Pros and Cons to each brand.
The optical differences between the NF and the MK4s are not going to be really THAT noticeable to most. There is a subtle difference only, I believe the NF has a slight edge mostly in lower light conditions.
The biggest difference between the NF and the MK4s is that you have the capability of having the reticle and turret in the same unit of measure with the NF scopes.
Why anyone would have Milrad reticle coupled with MOA turrets totally escapes me, but several scope makers still do this foolishmess.
ALL Nf scopes come with illuminated reticles, it is not an added cost option like the MK4s AND there is not another fragile turret put on the tube to house the reticle illumination switch on.
Personally the NF R1 reticle which is the most popular reticle NF offers makes the most sense being 1 moa secondary reticle markings, but I find it too busy so prefer the R2 which has 2 moa secondary lines.
The new Rapid Turn turrets I got a chance to play with in the field this weekend and am very impressed at how much of an improvement that is for long range shooting.
As Mildot pointed out we also carry Premiere Reticle and S&B both of which are fine optics, but nearly 2 times the $$ and are both Metric and 1st focal plane.
Having been born with MOA and 2nd focal plane optics have had a devil of a time getting my head wrapped around a weird unit of measure and the fact that the reticle gets bigger or smaller with magnification.