In the main I agree with R700. While it is true that my eyes are no longer 20/20 the fact remains that I cannot tell one whit of difference between the clarity of the NF benchrest and the NF NXS. Some of what follows may be interesting to you but a choice between these scopes will often be determined by (a) application; (b) personal preference; and, (c) budget. Here are my thoughts/observations:
None of the three are small scopes - The NF BR weighs 36 oz and is 16.6" long, the NXS is 34 oz and 15.9" while the Sightron is 28.9 oz and 16.9"
Internal adjustments (elevation) are NF BR 50 MOA, NXS 65 MOA and Sightron 50 MOA. None of these are bad numbers but if you are planning to 'get out there' you will need a rail that has 20 MOA or so slope.
The side focus on the NXS is easier and faster to operate than the AO on the BR - no surprise here - and stays set equally well. This is a plus if shooting to a variety of distances but irrelevant for F-Class where shooting is done at known distances.
The side focus on the Sightron is, as R700 says, not as good as NXS and is more "fussy" requiring periodic resetting.
The Sightron has a big advantage over both the NF offerings maxing out at a whopping 50 magnification but the NF at a 32 max ought to be enough for the vast majority of shooting applications.
Reticle choice ought to be guided by application - I have the Sightron with Fine Cross Hair for F-Class and the NXS with MLR for pretty much everything else. While intended application ought to be determinative sometimes it is what you like to see or are comfortable with or used to that will determine your choice. My feeling is that the MLR is more useful across a wider range of shooting scenarios that either the FCR or the NP2 DD but I must say that I may have made a poor choice with FCH for target shooting as NP2 DD is just about perfect for that application.
Click adjustments are excellent on all scopes - one-eight on the NF BR and Sightron is the way to go for F-Class but the quarter value on the NXS is better for pretty much most else and allows for easier math in calculating comeups when going from one distance to another.
While I think all are excellent/very good scopes the NF are simply better than the Sightron but it terms of value for money the Sightron is definitely one to consider. The differences between the NF BR and NXS are negligible but the NXS is certainly a lot more money - you pay for stuff you hopefully don't need like durability in combat and all that sort of stuff - but there is something I really like about the NXS and my next expensive glass purchase will be the NXS in 12-42x56.
Here is a crap cellphone pic of the scopes and their horses ( the other scopes in the picture are various Elite 4200 and 6500's - very good value for the money but not in NF league for glass quality and lacking the magnification power of the Sightron ).
Not that we were competing, but being guys we did anyway. Sadly I had my ass kicked by R700 and C3pppo today but I saved some face by producing this effort at 225 yards - not as good as those guys but at least I left the range with my head up a little bit lol !
Enjoy shopping for scopes !