I had this dilemma too and if based around damage both are similar. But mage only has table(near useless), cant bres, doesnt offer any cookies(not everyone needs int buff), also cant summon. As far as hero goes there are plenty of other classes that can hero. Plus no pet to tank elites.
Before I considered all this I was gonna try fire. And theres also this:
https://us.battle.net/forums/en/wow/topic/20769578557