After a couple of negative experiences with Vortex CS, I recently tried Athlon. My two Athlons are equal to or better than Vortex in that they are clear and bright.
For my eyes Vortex glass has a haze that I do not find with other scopes. When I focus on a paper target the lines on the target are surrounded by a blurry purplish haze and are not crisp. I find this result with Viper HS-T, PST Gen1 and to a lesser extent with PST Gen2. I do not experience this issue the several other brands of scopes.