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

it depends on which version you're playing... in The Shadow of Death, mages definitely shine, but if you take The Succession Wars into account, the balance is more or less maintained (warriors like Tazar, Mephala, and others can compete with mages/battle mages even without a spellbook). In any case, a warrior with the Sphere of Inhibition will defeat a mage (=

If I have the chance, I always level up a pure warrior:
attack
defense
magic resistance
archery
ballistics
tactics
pathfinding
logistics

+ the features of The Succession Wars provide good bonuses for such a combination of skills.