All in all we will be comparing current: Mark 4 6.5-20, VX-3 I mentioned above, NF NXS their new FFP 3.5-15, Sightron's 6-24 S-3, and Huskemaw's 5-20.
Once all is said and done, it will be written up.
Here is a list of things to think about when you check these scopes. I have probably forgotten a few things but it is some of the things about scopes.
1. Comparing scopes of different objective size is apples to oranges.
2. Exit pupil has little meaning but lots of people like talk about it.
3. As mentioned, the power multiplication should be the same or else expect to take it into a consideration as a compromise
4. The most critical aspect of dealing with a scope is to get a good focus with the eyepiece. Looking through a scope without a perfect adjustment of the eye piece is useless. Itís like taking a reading test with someone elseís glasses. Typically it takes me about half an hour to get a perfect focus. I like to use pine needles on a tree and dead twigs. If you can sort out individual pine needles at over 1000 yards then you have the blue green wavelenght transmission well in hand. If the brown twigs resolve well then you have the middle of the other end of the spectrum.
5. Visible light runs from red to blue so to check both ends of the scopes color transmission use some blue painters tape and some thing similar in red. Put this out about 500 yards or more and then see if it shades away into green or orange and or if both are equally sharp- unless you are good with colors you might need a woman to check this issue. You can look at it centered in the scope and then at the edge but remember you are dealing with a rifle scope not a spotting scope so edge is not as important as the center. The edge of the tape is where you will notice a color shift. I pretty much guarantee you that it will be there so look for it- there are no perfect optics.
6. Check the scopes in full daylight and then at 30 minutes after sunset or if you are an early riser before sunrise. I actually think morning is better because the ground in not hot and still causing mirage and you can work until the mirage gets to bad.
7. All scope should have a sun shade or none should.
8. Be careful about reflections up from surfaces such as a table or truck hood or even a stainless steel barrel. If necessary get some flat black cloth or paper to absorb and block reflections.
9. You will need a grid or else a set of perpendicular lines to check for astigmatism and for distortion. The grid needs to run through the entire field of view.
10. If the scopes have different power ranges select a common low power and a common high power. Do not use the max nor minimum of a scope, instead stay at least one whole power away from the each end of the magnification range. All optical devices are compromises and typically you detect the compromise at the extremes and the scopes perform best in the middle of their range.
11. Almost any cheap scope will look good out to about 300 yards. It is the 800 yard to 1500 yards that separates the quality of the optics.