Infiltrator, definitely. The only class that really matters.
I try to always have at least one infiltrator among my chars. It's just too damn fun stabbing people. 
Damn, still on my list.
Can infils duel other nobles? Can priests be infils at the same time?
On topic: not sure. Each class has their drawbacks and advantages, I suppose, and I've enjoyed playing Cavaliers, Heroes and regular Warriors. Just got into the Priest game, seems to have potential, but I have zero experience as Courtier or Infiltrator (playing since '09).
