I'm afraid the answer can only be summarized as "It depends" given the variability of map spawns. Post Awakening Kerry has the same attack speed as bandits but has a bit weaker attack power than Eunice or Mortimer outside of skill activation. That makes her strong enough to mash a basic goblin in one shot but not much else. Emilia needs outside support or her skill to 1 shot but she's considerably faster and her skill's initial timer is only 12.5-14.5 seconds depending on rank, so with the right placement she could plausibly have it up by the time the early packs have walked to her on many maps. It's a tough comparison because if the trickle of units is slow enough you might just want Call Reinforcements instead anyway. The whole thing makes me happy I have Thetis and can largely skip worrying about it.