Graphics wise is downgraded obvisoisly, but I've heard a lot of people here has GTA 5 and I've seen a post if I remember correctly that VGU has a GTA V clan going on so I figured it would be better if I play the pc version for now on since there more people I can play with compared to the xbox version. I have a bitch of a time trying to find people on the xbox version.
EDIT: I'm still installing the game so really I can't tell you a real, solid, difference yet until I install it but I imagine it will vary depending on a person's PC