Kevin is good, but I dunno .. he seems like he would fit the Sous Chef position better than Head Chef. Van has had some screw-ups, but not many and never like "YOU CAN'T COOK" type ones .. just the "What were you thinking?" ones. He also has gotten a lot of compliments from Ramsey.
I think he's hard-headed enough and skilled enough to make it. I would vote for Dave but the dude is falling apart. He has the skills though ...