So the SHV 5-20 and the NXS are both second focal plane scopes. That means that the reticle will stay the same size regardless of what power you have it on. That means that the reticle is behind the magnifying part of the scope and the subtensions (the dashes on the crosshairs) will change their value depending on where you are located in the zoom range. Their value will scale with the change in image. Example: the 10 moa dash would be 10 moa at 32 power but at 16x it would actually represent 20moa. 1/2 the power 2x the value. The nightforce scopes with the F1 in the name are front focal plane and the reticles values stay the same as the reticle is located in front of the magnification, it magnifies the reticle the same amount as the image so your subtensions are correct at all magnification values.
In this picture youll notice that for the First focal example that the reticles bottom dot is at the same point on the deer at all magnifications, cross hair centered on its chest the dot is on his hoof. With the second focal the bottom dot goes from way below the deer to up to the his bottom foot, it slides in relation to what you are looking at. [IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/theopticzone.com\/wp-content\/uploads\/2015\/03\/front-focal-plane-vs-second-focal-plane-rifle-scope-reticle.jpg"}[/IMG2]
Now, how does that effect you? If you have time and are capable of minor mental math you wont have any issues with a second focal plane scope. You just have to be cognizant of where you are at in your zoom range. If you shoot at low powers second focal is helpful in that you dont have to squint to see the reticle where as with a front focal it can get awfully small to make out. If you shoot at max magnification it also doesnt matter as youll never have to worry about the lower powers.
Lots of benchresters and paper shooters who shoot at known ranges prefer the second focal plane as they can often be finer crosshairs enabling more precise aim points and they know the distances they are shooting at and thus they know what they need to do.
Steel shooters like the front focal because they can use it on any magnification and what they read on the reticle is what they need to adjust, no mental math or having to worry about compensating for what zoom you are on or at what distance. It you miss by 2 mils according to the reticle you need to dial up 2 mils, end of story. No worrying about distance or zoom.
With that said I doubt you would be let down by either the 5-20 SHV or the 8-32 NXS. But if you are wanting to do the "tactical" scene a front focal plane scope makes a whole lot of sense for the running and gunning PRS stuff this site focuses on. Go over to Accurate Shooter where its F class and Benchrest guys and youll get them telling you to go second focal plane.
