If you want to get a basic grasp of the language quickly, I'd say Japanese is best. If you learn the 50 basic Hiragana, you can write anything and be understood, and read basic things, and that can be done in under a week.

There's also no tones in Japanese, and vowels are always pronounced the same, so if you get the 50 sounds correct, you're 90% of the way there.

But I think Chinese is easier once you get over the initial hurdle, the grammar is a bit simpler. If you aren't in an environment where you can practice with native speakers, go for Japanese, otherwise you'll never know if you're getting the tones right!

And anything imported from overseas to Japan since about the '50s is pronounced phonetically, so you can get an instant 500+ words of really easy vocab by guessing things like:

su-ni-ka = sneakers

ma-ri ku-ri-su-ma-su = merry xmas

etc

But give the podcasts here a try, and some Japanese ones, see which you prefer, and good luck either way. But don't try learning both at once, they get lumped together as one language!