Just so you are aware, MU is not the only FB/Skyteam partner in China. You also have CZ (China Southern), MF (Xiamen) and Taiwan based CI (China Airlines). If you do a lot of domestic or regional travel, you can take good advantage of your FB membership.

I'm in the fortunate position of having top status in all 3 alliances, but I even if I wasn't I would choose the best timing first, then the best seat second, and best services third for such regional routes. It's true that NH, JL, SQ and CX are mostly excellent airlines, but they each have their niches and of course do not fly domestic routes in China.