I've always favored learning European languages because they are linguistically related to English, and it strengthens English use as well. For example, knowing French and Spanish, I can often decode unknown words with roman root words in them. Handy in medical and academic settings. It was also very handy when I worked for a business with lots of Italian speakers as I could understand most of what they were saying. I'm not sure that mandarin would allow you to decode other "close" languages or whether there even are other close languages?