Dwarf vs. Wingayel (Lands of Outcasts)

Three level 5 spells? Okay, I understand if we're talking about rushing or at least the mid-game, but it definitely won't help in the late game. But Black Magic will help, since that spell is level 4 and requires less mana. Look into the details and you'll see that even Stopping Cold deals 30+30*magic damage at expert level, while Black Magic at expert level, after killing one Paladin, deals 360+36*magic damage. So, which is more effective?