What is the difference between the two versions?

They are two different games,two different worlds in the same universe.

As far as we know,the only common thing is that their storylines are infuenced by the presence of crystals.Other than that,FFvXIII is a much darker take on the Fabula Nova Crystallis series of events and its an action game in the style of Kingdom Hearts.

They are two different games. They both take place in the same universe, but aren't related other than that. You could think of Versus as a spinoff, but I wouldn't. Versus will be using a real time battle system similar to Kingdom Hearts, while FFXIII will be using the ATB battle system. They have two different stories. So yeah basically they are two different games. Not two versions of one game.

Ask me again in 2010 when they finally come out!

This question willl never die!!!

There are two different game with different characters.

everything.

they share some mythology and world but they are both full front square enix FF JRPG titles

VErsus are not only char design by nomura but also directed and being done by the awesome kh team!.