Lets examine what evils get as opposed to goodies:

1) allies who don't suck (I love the fortress, I really do, but I've seen some horrible things from members of the Fort)
2) the ability to kill off more than 1/3rd of the NPCs in the game while remaining in role
3) the ability to kill off people who are hoarding all the equipment you want, instead of having to hug them and walk away.
4) far less role restriction: an evil can kill anyone he wants, ignore almost anyone he wants, and has much more latitude over his actions in general than a goodie ever will, even without the cabal dynamics coming into play.

Its no coincidence that on average, evil pk ratios are much higher than good pk ratios, that the majority of the playerbase plays evils, and that all the characters in the game with the best pk ratios are, gasp, evil.