I would add a few comments:
1) At the age of 23, you are really young for the legal profession. No need to worry about how old you will be after a few years at school.
2) Between LLM and JD, which one is better? If you want to stay in the U.S., JD is better (but see 在美国读 JD 须知 shown above). If you want to go back to China and you may have financial difficulties to pay for the JD study, choose LLM.
3) Nothing is certain for your career. Just pick one path that seems to match better with your aspiration/financial conditions. Every path has its own pros and cons.