With the exception of the Silva fight, Vitor has traditionally gotten worse as the fight progresses. if things don't go his way he fades and folds. ie - Saku, Couture, Jones.
Interestingly enough, Weidman isn't great in the late rounds either as shown by his recent fight with Machida. Machida has some power but not the power Vitor does. Machida tagged Weidman enough in the late rounds when Machida started to come on strong.
So if Vitor can overwhelm Weidman early and set his game plan up I see him taking the belt. If Weidman weathers the storm and decides to take Vitor down and grapplehump Vitor, then Weidman will break Vitor like Couture did.
In this fight it's whoever brings the right game plan. I have to give it to Weidman because I see him frustrating Vitor and Vitor falling apart as a result. But Vitor will hurt Weidman like no other fighter has before.