Glass quality wise My vx3is are a bit clearer but I believe that's due to them being newer and the vx3 have hundreds more hours hunted with, dirt, dust, water, grime on the lenses over the years... with that being said the vx3 finish seems a shade more durable than the vx3is I have.
These people talking about how poorly the vx6 track can come watch the next time I take my WSM, RUM and 300WBY past 1000. Anybody in the southern middle Tennessee area can shoot me a PM if interested.
I have 2 nightforce NXS I have had swaros. The leupolds don't beat the NXS IMO as I prefer the MOAR to the leupold T MOA but that's kinda subjective.