A war of attrition is one where two sides essentially grind against each other and the winner is the one which lasts longest. A decisive battle is one where a conflict is won through a single, acute encounter where, due to either demoralizing or circumstance reasons, one side gives up. It’s the knock-out punch vs. the fight to exhaustion.
When applying this dichotomy to competition, we need to be careful about who we define as competitors.