<p>Why are you just picking between French and Spanish? There are many other languages out there. Of course, it all really depends on what you want to do. Spanish is the lingua franca of Central and South America, if you have an interest in those regions, it’s a very good one to learn. Unless you have an interest in those regions, though, Spanish is a low value language, it’s not an important language for international business or diplomacy, and it doesn’t open much history to you.</p>
<p>French was, once upon a time, the principal language of global business and diplomacy, but has since been eclipsed by English. That said, it retains an important status as a working language of the UN, etc. and an official language of 29 countries (and an important language in several others). In every region of the world other than the Americas, you’ll find more French speakers than English speakers, and many of the countries where French is spoken are richer and more involved in business and diplomacy than the Spanish-speaking nations. French also opens a lot of avenues for historical study that Spanish does not, as it was long the language of diplomacy.</p>
<p>That said, I’d encourage you to think about some other languages as well. If your primary field of interest is global business, think about German - Germany is one of the world’s dominant commercial powers and many German firms are incredibly important in international business. You might also want to think about Japan - Japan is again an important economy, and given that you already speak Mandarin, picking up Japanese would allow you to market yourself as able to do East Asia generally (of course Korean would be helpful to in this respect, but one step at a time). Finally, it might be worth learning Hindi - China and India are the world’s most important growing economic powers (and largest nations) so being able to do both is great - of course Hindi isn’t spoken everywhere in India (and is less dominant than Mandarin in China) and English is more common in India, making Hindi less essential but it’s still probably the 5th most spoken language in the world. You can also walk Bollywood without subtitles :).</p>
<p>If your interest is in international security, then the essential languages to think about are Arabic, Farsi, Russian, and Urdu. All of these are also “critical needs” languages, which mean that if you can speak them (and are an American citizen) you received preference in hiring for the State Department, CIA, FBI, and other agencies focused on international affairs.</p>
<p>On the whole, frankly I would advise against either Spanish or French. People who can speak English and Spanish or French are a dime a dozen. People who can bring less common languages like Japanese, Hindi, Arabic, Farsi, Russian, Urdu (and many others including Korean, Turkish, Indonesian, etc.) to the table are much more valuable to potential employers. Academically, these languages are more challenging, but they also open the doors to research you might not otherwise be able to do.</p>