Each to his own, I guess. If I still played FFXI, I guess I would've been a Paladin with Warrior as a subjob. That's the best fighter class, imho. Ninja is also good, but I don't like ninjas outside FF and they're way too expensive anyway. So it would be either Paladin or Black Mage for me. White mage would get boring rather quick, even though it has its advantages.

Paladin or Black mage.