For the most part, we would say that Eve isk affliction enhances killing speed in general PvE, that is to say grinding, leveling, dailies sand so forth. It focuses on our DoT's and allows you to drain tank monsters basically ending fights with 100% life/mana. Demonology enhances survivability without truly sacrificing much DPS comparative to other builds while leveling. However, the differences for those fully fel-guard specked will become more apparent once you hit 70/start PvP or PvE raiding.