I would have to say Drake is way out in front at this point. Kratos never did bring us that Multiplayer DLC like I wanted. Drake with his thriving online community and awesome multiplayer offerings have left Kratos in the dust. Single player fanboys have hurt the title with there archaic single player purity notions.
A point I would like to make is that Kratos was the clear face of the brand until Drake showed up. Kratos needs to challenge Drake if nothing else we gamers benefit from the rivalry.
I think Nathan Drake is, because his games are better and the characters are better developed and the story is amazing. Kratos is awesome, but his games just aren't as good as the uncharted series. So I think Nathan Drake is the face of Playstation.