I had a chance to compare my 10x50 Vortex Viper HD against a 10x42 Swarovski on an elk hunt last week.
The Viper was within a very, very small margin of equaling the Swaro in optical quality (sharpness). What I did give up with the Vipers was comfort.
I wear glasses, and I could pick up the Swaros and immediately look through crystal-clear glass. The Vipers took some jiggling around to to find that "sweet spot" in positioning the eyecup perfectly in front of each eyeglass lens. This happened every time I picked them up. Those who don't wear glasses can often put the eyecups repeatedly in the same place by pressing them into the same place against the eye socket or the bridge of the nose, but I find that with glasses, you just scoot them around until it's clear.
Anyway, I love my Vipers and they have excellent glass, but if I had the money, I'd buy the Swaros.
