Comparing vampires to champions is absolutely wrong—there's a two-level difference. If we judge it that way, then death knights are much stronger than crusaders (the same two levels). Regarding the fast start—skeletons are stronger than spearmen at least in terms of numbers. However, archers are stronger than zombies, and that is already significant. Third level—griffins against wraiths are much stronger, I agree. But vampires against crusaders—this is debatable. Vampires resurrect and fly, so I think the advantage is on their side. Fifth level—liches against monks. Both units are ranged, but liches deal area damage, and that is where their superiority lies. Champions against death knights. The most interesting duel, but death knights are easier to build and their bonuses are much more substantial than those of the champion, which effectively only works once. Angels against skeletal dragons. Here angels look stronger, but also more expensive. On maps with a shortage of resources, undead clearly seem preferable. But if humans can make it to angels, then the forces even out.