What advantage does Riviera claim to have over Wintermute? Do you think this is true?

Riviera says that Wintermute has underestimated him, because he has something that Wintermute will never understand--a perverse nature. I do not think this is true, because Wintermute chose Riviera for very specific reasons. Wintermute is also a super-intelligent AI, while Riviera is an egotistical drug addict.