If you already have large balances on AAdvantage you may want to think about crediting CX to that account. However, three years is a long time and CX often will match status, especially if you have just moved to Hong Kong. You might want to review the AsiaMiles threads here for a better perspective.

Transferring miles to AAdvantage one account to another costs a huge price, it's more like buying them than transferring them and is limited to 60k miles per year anyway.

Will you likely manage to concentrate on Marriott properties or should you maybe have accounts with one of the other chains. You would benefit from examining where you'll be traveling, what hotels will be most convenient, and choosing your hotel program on that basis rather than simple program optimization. You'll probably end out with lots of variety anyway if you'll be traveling frequently.