Nothing, and that's the issue I have with it. There is nothing unique making me want to be a pirate even tho the selection screen would try to indicate otherwise. They are bland nation clone.
Worse are the pro pirate players who attack the anti status qoue players for being afraid of pirates, or not wanting the challenge of having pirates in game, when in fact it's the opposite.
The pro status qou pirate players don't seem to want what the devs intended, but rather to have a black flag and that's about it. Whether it's fear of not being able to hack it or something else I have no clue.
But given the pirates were supposed to be the " hardest" faction and instead we got what we have now, it's safe to say I'm really disapointed in the dev team in regards to this aspect of the game.
Currently there is nothing to indicate that pirates are the hardest faction, but I would love for someone to prove otherwise( if they can)