The eternal question: which heroes are better, mages or warriors?

I used to really love maxing out all the magic skills for every hero, even a Knight... but then I realized it was pointless, and he would hardly ever become a good mage under any circumstances. Now I usually play depending on the situation, but I prefer to have one maxed-out mage and one maxed-out warrior in my army. And then, which one is better depends on the enemy and the circumstances.