Which monster do you like the most in Heroes 5 at level 5?

In general, comparing a hydra to a unicorn is very difficult. They have different purposes. Hydras are tanks, excellent defensive units; the enemy reaches your side of the field and doesn't even consider attacking your slow hydras. And when their turn finally comes, there's a chance to attack two or more units without retaliation. Plus, attacking a hydra is quite costly (especially a dark hydra). A unicorn, on the other hand, is an excellent offensive unit with a useful ability.