I asked the same question about Leupolds (Differences between the 03 and 04 models). This is the response I received from Leupold. I cut and paste this out of thier email to me.

"The big difference between the '03 model and the 04 VX-II is that in '03 only the outer lens surfaces were multi-coated. Now all the lens surfaces throughout are Multi-Coat 4. This results in a little more brightness."