I don't think there is a "universally correct" answer here.
Pride: Always works, even better when at low HP
Vigor: Ridiculously powerful at high HP, but you gain zero if you drop to 50% or below
So, which one is better will depend on content and your team. Most of the time Vigor will be better, but if there was an Amaru that takes 10 turns to kill, then you wouldn't want to bring Vigor for example.