A very nice review with great pics. Thanks!
I just purchased the Vortex Viper 15x50's and so far am very happy with both the optical and build quality. I have use these with glasses on and off and both ways work great without any blackouts.
These have a little less FOV with 210' @ 1000' feet. Lighter weight at 27.2 ounces and a close focus of 8.2 feet.
I think a couple of the main differences is that the Kaibab is listed as having silver coated prisms although both are phase corrected. The Kaibab also, I believe, have a different lens configuration (as does the new swarvision?). Both are using XD or extra low dispersion glass with full multi-coatings.
With $1,200.00 versus $600.00 I decided on the Vipers.