One "acid test" for quality binoculars is;
"can I look through them for hours on end without eye strain".
I can keep my eyes on my Minox 15s all day long, no problem.
Optically, very good. I have never played with the Vortex Kaibabs, but so I can't compare them, but the Minox work very well. The only draw back is they are kinda heavy and big.