WELLLLLLLLLLL, I have about determined that a 40X is about all the magnification I want so I would go with a straight 40X and the lightest one. I don't know what the warrantee is on the Nightforce but that might be a consideration as well. Some of my friends had problems with their Nightforce scopes back a few years and got away from them but I haven't heard anything adverse about them in some time now.
It is the opinion of a friend, who knows a lot about optics, that rifle scopes do not need to be a big as they are. He believes great smaller lenses would transmit plenty of light, for our purposes, ergo lighter and less weight up high on the package. Considering we usually don't compete in near darkness, that seems to make sense to me. Some of the clearest and brightest scopes I have looked through are some the old Leups and small lensed ones. Unfortunately, the tactical folks don't seem to be concerned about size or weight so we are to some degree, the victims of the design and marketing directed their way.