I've heard from most reviewers that the XBox version is better simply because of the performance issues on PC. My brother and my friend are both playing it on PC, and it looks fine to me! Either way, the XBox version has a better menu and combat interface system, that's for sure. Despite that, both versions still offer the same gameplay and the same story. That's what made the game on XBox. If you haven't played it on XBox, go buy one, and play it.
If you own a good PC, then play it on PC if you don't have an XBox. This game is one that should not be missed, trust me.
-Lasereth