Against which factions is it easier for demons to fight, and against which is it more difficult?

I think things aren't that simple with humans; I remember once playing against an opponent who had a hundred paladins (both armies were almost equal, but it was a significant imbalance), and my jaw dropped. However, the main thing is not to overdo it. And demons don't have much power because humans rarely have more than a hundred mana, and heroes are mostly warriors, not mages.
Against Orcs, the main advantage is Dark magic, especially Berserk, Dispel, Subdue, and even Seduction from succubi. And if you manage to get Cursed Land, mmm, that's great.