Kydex is better from some guys than others no doubt. Not all kydex is equal either, I've had some that was too thin for my taste.
Kydex is great if you plan on swimming or diving or washing it etc.
Leather is great, beautiful, smells good. Kydex isn't junk though, it has its place. It is also much less costly.
Also, if I went to say Iraq. I would rather have a pistol in a nice Blade-Tec holster than leather.