Hey Kevin,
Having learned four languages over the years I would echo John's advice: Learning any language will be a benefit for not only your MI career, but the remainder of your life.

I would take Russian over Chinese, although both are good choices and will serve you well. I disagree with Brian - There are more than 170 million Russian speakers and 2 million living in Germany alone (just a tad behind Arabic speakers in the world).

We could argue that there are five times more Chinese speakers than Russian, but keep in mind that the geographical distribution of Russian is far greater being the second language for many people in Europe and the former East Bloc.

Good luck with whatever you decide !
Regards, Stan