I am looking at purchasing my first set of 15x binos, and even though I love my Swarovski 8x56 glass I plan to give Vortex a try on this purchase. Great warranty, good reviews, and low price points. What I'm having a hard time deciphering is the difference between the Viper and the Kaibab. The latter has a somewhat bigger objective, and one would assume better glass since it is about twice the price. But they both feature low dispersion glass, so what is the real difference? And is the performance advantage of the Kaibab worth paying double?