The point that gods can be killed is rather moot unless Dante gets his hands on Pandora's box (which Kratos needed to be given the power to kill a god. There was no way for him to kill Aries otherwise). In his God of War form, Kratos would be nigh unstoppable. He's going to be far more powerful than Dante, and pretty much be an expert in all forms of combat. Kratos hands down there.

Assuming we're talking regular Kratos here, it may be closer, but being trained by the God of War, as well as being given numerous weapons and abilities from other gods leans things in his favor. There is one major reason I'll give it to mortal Kratos over Dante though: Aries actually killed Kratos just after getting Pandora's box, but he still fought his way out of the underworld to go on to kill Aries. Even as a mortal, nothing will stop him, not even death.