The type and shape of lenses. The VX-2 optical system is a descendant of the Vari-X II with incremental coating updates. Same as the VX-3 is a descendant of the Vari-X III.
Putting fancier coatings on a Vari-X II doesn't turn it into a VX-3 any more than putting Rainguard on it turns it into a Bushnell.
Ok. I wasn't sure what you were getting at. I'm not sure if there is a difference between the actual grade of glass itself between them either. I know that I bought a VX2 4-12 from SWFA a little over a year ago and I am happy with the optics in that scope.
