Here you can see a list of companions that a pirate has (thanks to dittomonster.com):
See? They are all diferent, and the companions also have classes, the Privateer is the class where you get more companions. Your first mate will be the one who will run side-by-side with you and will always join your battles.
If you level up you companions they will gain a more cooler look, what are you waiting for?
Level up all of your companions, even the ones that you don't like, and you will have a super crew, good luck!!