The former determines if there will be a swarm of competitors. (If entry barriers are low, anyone can compete.) The latter determines whether there will be detrimental competition. (If exit barriers are high, competitors will fight to the last penny.)
前者決定是否一窩蜂（進入障礙極低，人人可以參加），後者決定是否惡性競爭（退出障礙極高，罷手血本無歸）。