I think over all:
Rogue/sin #1 if you play alone a lot, etc. You can get to bosses fast (drain etc) and gear up easier, etc. Sin can pwn solo and if ur out matched vs or party u can usually continue playing where as other classes once they are out matched have to wait for better pty, help, or log out of pk. The only downside to sin is the exp if you don't have people to exp with. DS is usually the best to exp on but as soon as one or more rogues are in that party most parties won't allow more rogues and prefer warriors.
If you are a geared up warrior and you have good people to play with, this is a great easy class. Crazy def and hp at high levels (having crazy hp and def does not make you a great player lol) and very few skills used compared to other classes. Inter server wars Warriors were the most powerful class by far. Warrior is def fun if you have the gear but if your a glass jaw it sucks. Warriors are also great to exp up since they pwn at DS and Paramun and are chosen over other classes in number, etc.
BP is awesome and wanted all the way through exping and pking. Good bps are hard to come by since many do not know when to be support and when to attk. Also a lot of bps that don't have the necessary equipment should really be tank support because they just end up getting everyone killed.
Mage only if u have fellow mages otherwise you have to have godly items to solo. It's also tough to boss as a mage and build up and later the only thing really worth exping on is EW and that is raided all the time which can be frustrating out of you mind.
My 2 cents...