Should I learn Chinese or Spanish?

I'm still undecided whether to take chinese course or spanish course. I know Chinese and Spanish are becoming worldwide languages because almost half of the world population speak these languages. It would definitely bring me benefits if I could speak these languages fluently. I can speak Korean, English and a little Spanish. I know for a fact that nearly everyone will speak English fluently in future, so it wouldn't give me any advantages of speaking English. In order to become successful, I have to learn another language besides English. Since Chinese and Spanish are the most widely spoken languages in the world, I want to learn one of those languages. What language should I learn, Chinese or Spanish? Please give me reasonable suggestions! Thanks