Which creatures from the alternative upgrade options do you choose?

Nah, the new hydras definitely rule, because the old ones, with their tiny initiative, don't really have time to regenerate, while the new ones can deal some serious damage to the enemy. I was playing once, and I attacked a Utopia of Dragons with a hundred hydras, and seven Emerald Dragons attacked my hydras. Five of them died from acid, and the remaining two died from a regular counterattack.