Hmm... Tough call. Let's do a little comparison, shall we?
Here's a Pirate:
Statistics:
Ate a Gum-Gum Fruit, Super Stretchy
Likes to have fun
Wears a straw hat (Big advantage)
And here's a ninja:
Knows all sorts of "jitsu".
Determined, not willing to give up.
Has the soul of a demon that attacked a village.
You know, I can't really tell which one would be better, or stronger, for that matter.