As often happens with this type of Plinky prompt, there needs to be a third option... "mutually fatal tie" ... b/c in my mind it all comes down to whether the snake is poisonous or not. If the snake is not poisonous then I'd bet on the kangaroo 9999 times out of 10,000, but if the snake is poisonous then it's quite possible that it would get a good solid bite into the kangaroo's hide before the kangaroo ripped it apart. The snake dies either way; the kangaroo also dies, but only if the snake is poisonous.

Regardless though, the kangaroo is cuter.