It all comes down to experience in the end. Pyrrha was a prodigy, so she might have gotten a few good hits in, but I'm sure she would have lost against Raven eventually. On the other hand, she would never have allowed her ego to make her underestimate her opponent until it was too late, like Cinder did. I'd also like to think that Raven wouldn't have killed Pyrrha if those two had to fight each other for the relic, but that may be too optimistic of me.