Barbarians are strong on small maps, Chaos and Order on medium (I've played Nature little), Death on large (this is a generalization, for example). And Life doesn't stand out anywhere, IMHO.
Level 2 + the building for the 3rd + the 3rd level itself. And what about others? For those same Barbarians, a Stronghold is needed for harpies, and a caravan for nomads. For Nature, a Ranger's Guild for elves, and a Grove for tigers. And then, for unicorns, the Fountain of Luck (I think, I don't remember exactly), and for griffins, a Stronghold. Draw your own conclusion.
P.S. Unfortunately, I can't play with you right now, but I would gladly prove to all of you that Life is STRONG! IMHO.