You have to understand something about the way those mixes are approached. Primal Fear is mixed with the guitar being the focal point. Silent Force is all about DC Cooper; it's his band/brain child, and he is the focal point of the mix. Everything is manipulated as they see fit to make room for DC Cooper.
Not the way I would mix, as I prefer a slightly more balanced or leaning-towards-guitar mix (of course), but I give DC Cooper all the props in the world. He is a phenomenal singer and VERY few singers out there can compete with his chops, talent and effortlessness, Scheepers included. Scheeper sounds like a cat in a blender compared to the richness of Cooper's vocals.