Interesting match-up. Gun to my head I'm picking Cutelaba, though. Walker's only notable win against a grappler was Cirkunov who he clipped with a flying knee in the first round before Misha got his takedown game going. Anderson and Krylov both were able to take him down and control him. Spann had some success against him in the grappling, too, but got overly excited and was the victim of bad fight IQ (along with possibly some back of the head shots?).
I can see Cutelaba going forward recklessly and getting clipped, but I want to believe he's learned some lessons from his previous losses. However, wild strikes on the entry (or at range if Ion can't make his way in) is really the only thing Cutelaba has to worry about. Walker is not much of a submission threat historically. Cutelaba's cardio has improved significantly and Walker doesn't have a history of winning long wars of attrition anyway. Conversely, Walker is at risk of getting chinned or wrestlefucked here at any given moment in the bout... so I guess I'm going with Ion. But really anything can happen considering both guys are wild to a fault and the first round is their most dangerous.