Hmm... I'm almost leaning to playing as a Mage, just because you can tell by the way he handles himself that Prospero is like some kind of a magical pimp.
The thieves so far look like a bunch of sniveling cowards, while Kurdt and the brigands look like swaggering badasses.... plus they got whores! And they mock the thieves as getting punier jobs than they do.
I'll probably do a "pure bastard" thief run, and then a "somewhat-good" (or as good as you can be in a game where you seek infamy) Mage run. Or.... I don't know. If the thieves get badass after meeting the boss, I'll stick with them but if not, I'll go with Prospero.