While I haven't watched many shows... I would think clay will probably win.
I really don't think that either one of them have the "Pop" sound to them... Clay is "Mr Broadway" and Ruben is "Mr Love Song" and while neither of them "look" the part, Ruben IMHO is farther away looks wise than Clay... Now, if Ruben was a Rapper, that would be a different story, since they have different criteria.
As far as stage presence... I don't think either one of them have it... they both just stand there... and todays "Pop" audience wants cool dance moves and such. Unfortunately, it's not just about the voice, it's about appearances...