Unfortunately, the ninjas would win. The pirates would only stand a chance if they pulled some stunt qwith canons hidden behind packing cases.

However, if the question is, a group of ninjas and a group of pirates are in a bar, who gets the girls? then its the pirates every time. The ninjas would all huddle in a corner bitching to each other about who does the best onhi-momi-gomi like the big nerds they are.

That's why its better to be a pirate. Fighting is OK but girls are better.