I've thought about this match up a lot actually. It'd either be one of two kinds of fights, either an explosive one, or a chess match due to the level of skill they both have, and how they are both predominantly counter punchers, especially Rigondeaux. They're both lightning quick of both hand and foot. Both have tremendous power. The defensive advantage goes to Guillermo IMO.
Very, very hard fight to call. But I'd probably give a SLIGHT advantage to Rigondeaux due to his better defense. I think it'd be an either 12 round tentative chess match, or an explosive short fight. I'd probably go with Rigondeaux with a late TKO, in a VERY close and chess match-like fight.