Simply stated, li goes for the immediate hit, while shi seeks first the positional advantage of the setup. The former is the aggressor racing against time and who in his directness risks becoming overextended, stretched too thin, and thus vulnerable to the counterattack. The latter, the nonaggressor, with no need to rush, puts time on his side, even to the point of ceding an unimportant clash now in order to come back all the stronger later on.
