Why are you phrasing this as either-or? We don't need to decide whether a hammer or a screwdriver has a "higher marginal benefit", we use both as appropriate. Cooperating is conditional on it being useful, sometimes it's a good idea and sometimes it's not.

Getting back to Overwatch, there are cases where you need to grab an assassin and go hunting for the enemy sniper, and there are cases where you need to be a healbot and just stand behind your tank...