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

Mammot, I'll try to refute your arguments in favor of mages.

Actually, I wasn't arguing "in favor of mages." Personally, I prefer warriors. It's just that this follows from my experience: you can never have too much mana! But what to spend it on is another question.
As for restoring mana in cities, wells, and magic sources: depending on the map, there may be few of these objects, and they may be located far from each other and from the place where the hero is now. If you've been traveling somewhere for 2 weeks, you're unlikely to be inspired by the prospect of restoring mana by jumping into your home city and then spending another 2 weeks returning to the same place. Have you played the "Royal Reward" map by Green Drekon? Try it, and you'll understand.