Thanks. Appreciate the input. I was kinda leaning toward the 4X myself, b/c of exactly what you mention ... glass quality, but I'm sometimes tempted by what 6X can do for my 63 yr old eyes.
Truth is, most of the scopes I've purchased in the past 10 years are so far superior to my 30 yr old "premiere" scopes of yesteryear that I find everything to be an upgrade ... almost.
When my son's 6X comes in (ordered it for him yesterday) I'll give it a good look at his gun range in fading light, and then chew on it for awhile before I decide. I'll meanwhile look for a gun shop that might carry both for my observation.