VX-II (roman numerals) were phased out several years ago in favor of the VX-2 (arabic numbers).
There have been several upgrades in recent years. The VX-1 is an improvemnent over the older VX-I. Starting in January of this year all of Leupolds lineup was upgraded. The current production VX-1's are pretty good. I have a 2012 model VX-2 that is better than a 5 year old VX-3. I'm sure the VX-3's are improved as well.