I too am located in China and kept my Delta skymiles account as my primary. I mainly fly MU, and occasionally CZ when it's more convenient. Xiamen is supposed to be a good choice too but they don't have many options from my city so I can't comment on them.

MU isn't great but they always recognize my ST elite+ status and I never have a problem getting into the lounges on international trips. The 100%mqm earn is nice too.