Chinese vs. Japanese

Okay so. I've planned to learn an Asian language, but I'm stuck between 2.

These are Chinese(mandarin) and Japanese. I know its sorta biased, but can you guys give me an indication of which I should learn?

I want to go to either country and teach english as a second language, but which would be more "opportunistic?"

>>7
Chinese won't take much longer to learn than Japanese, they take about the same time to achieve proficiency.
http://en.wikibooks.org/wiki/Language_Learning_Difficulty_for_English_Speakers

OP, I'm currently learning Chinese.  It is simply going to be more useful for my career and is a better investment of my time.