The difference between governing a 10-million enclave (a significant proportion of elite refugees among those 10 million) that serves as a forward outpost to a friendly superpower, and governing a war-ravaged empire of ~600 million (in 1949) - subsistence farmers most of them - seems to me greater than, say, the difference between running a coffee shop and Northrop Grumman.

Very well, you can make that argument. So I'm taking your answer to my alternative history scenario:

Suppose China was divided in half between Mao and Chiang and they manage to avoid war for several decades due to cold war dynamics similar to the one that kept a divided German and Korea stable. In 2000 which half of China would you expect to be the better developed one?

Is that you don't expect the capitalist half to be significantly better off than the communist half?