There are three things about the FX3 that makes it preferable for me over the FXII.
The FXII's don't have finger tip adjustable dials which I find useful. The FX3 does.
The FX3 comes with Leupold's super tough Diamond Coat 2 coatings. That alone would make the extra money worth it to me.
The FX3 will work on the darkest nights. Nights, not twilight or "bright, clear" nighttime conditions. Since I do alot of walking to and from my hunting areas under nightime conditions, I insist on a scope that will work for me at night. I might add if you have any loss of night vision, which is common after the age of 40, this may not apply to you. E
