I have the 3-18 x50 non HD that I bought on closeout last year. Always wondered what I gave up vs the HD model in terms of glass/coatings. Seems you have both, what have you noticed in terms of diffrerence in clarity and low light performance?
Sorry about the slow response but it was a matter of getting things in the same place at the same time.
Checked VX-6 3-18x50 ZL against VX6HD 3-18x50 ZL2; focused on a white sign with black lettering approx 3 inches high at 675 yds in fading light. Clarity between the two scopes appeared little different to indistinguishable. This was no high tech check, only metering instrument being the eye; my own at 62 years old and my son's at 16. Interestingly we both use the "0" diopter setting and ended up with side focus set at the same point (distance) for best clarity on both scopes. From my perspective the primary advantage of the HD version over the original is that if you are shooting past 1000 yd ( not me) you have the ability to dial it, 20 moa on the original only just gets 7mm wsm to 1000 with the right load, projectile, and zero range. If you are in a circumstance where you have time to dial windage, or want to shift it to suit a different load in a field situation you can do it without the possibility of losing your original zero. Other than that the flip caps would be great for some, but not necessarily for me.