For me, I’m interested in the scenario where Japan has relatively unlimited resources to crush you (in terms of planes) and a handful of infantry. So you are balancing your goal of maximizing the probability that you will kill that one infantry, versus preserving your infantry for the 2-4 turns that China can expect to live by retreating.
This is typically in the first 4 rounds of the game when China is retreating/generally getting crushed.
Would hit with 2 then, but again it depends on what else Japan has to hit. Their resources are not always unlimited (e.g., Russians, British, Americans in play)