Which faction poses the greatest challenge for the Dwarves?

For Mish-gan: Why then, during the anniversary event, aren't all players choosing to play as Humans? Probably because they can be rushed, and it's actually possible to train a large number of Paladins, but only on large, resource-rich maps. And by the way, having many horses doesn't guarantee victory; there are spells like Blindness, Charm, Berserk, and Holy Vengeance.
Starting as Igvar is fast, but not reliable. You'll almost certainly suffer losses on every neutral creature stack, even if it's just a few. Although, maybe on Veteran difficulty, you can clear them without significant losses.