Since it's been determined that it is much easier to train to become a pirate than a ninja, the next question is which of the two gets you more street cred?
1) Movies. Ninja movies are notoriously terrible--Chuck Norris' "Octagon" was about what you'd expect from a man who is mostly beard and fist. And the "American Ninja" series had the distinction of teaching us nothing about Americans or ninjas. To be fair, though, I've also never seen the "Pirates of the Carribean" films, since they're based on an amusement park ride and I refuse to see movies based on rides ever since the flop "Ferris Wheel of Death 2, Electric Boogaloo". But "Princess Bride" had the Dread Pirate Roberts in it and that was pretty good, so point goes to pirates on this one.
2) Song. Apparently there was a musical out called "Pirates of Pensance" (sp?) and there are a number of old Irish drinking songs that sing of the glories of piracy. Let's face it, those long ocean voyages have one simple effect on you, besides scurvy--a lust for song! Ninjas, on the other hand, are terrible singers. The closest thing to a singing ninja I can think of is Grace Jones and I can't even remember what she sounds like. Point goes to Pirates.
3) Liquor. A number of pirates have had liquor named after them, from Captain Morgan, to Jebediah "Redbeard" Jagermeister. Ninjas, on the other hand, have not had a single drink named after them, even though it was widely believed that Adolph Coors enjoyed dressing in black and murdering people silently. Point goes to pirates.
4) Fashion. Ninjas do have a lot of copycats, from girls who wear black leggings (seriously, what's with that trend? Did someone find it hot?) to the "goth" and "emo" movements of the '90s and beyond. Yes, black is a slimming color! Pirates on the other hand have not seen their type of dress catch on. If you wear a puffy shirt or a tri-corner hat in a bar, people will think you're a "pickup artists" trying to "peacock" and "attract attention" from "ladies". But no one dresses like a pirate unironically. Point goes to ninjas.
5) Common expressions. We've all heard of "pirating" software, but have you heard of anyone "ninja-ing around"? Nope, point goes to pirates.
Looks like from a cultural relevance point of view, the pirates win this one.