I have both Magicka and Stam nb. The stam build definitely pushes out a lot more dps, but I find it has less sustain than the magicka one. Because of this I tend to play more offensively with my stam (kill it before it kills you), and defensively with magicka. But it all depends on whatever play style you enjoy. They both work, which is why I never understood these types of questions.