Well, just like in ASB those who import the JP version can't play against US players. Especially since the NA version is PS4 only.
The PS3 version got the short end of the stick. Both in terms of graphics and stability. Some framerate problems may occur on some stages like when Joestar Mansion sets on fire. (This may be just online, i forget exactly).
Not to mention that PS3 PSN runs worse than PS4's. For NA, 1v1 matches seem to run okay, but 2v2 are in desperate need of a netcode patch. This is only going to be worse when playing on JP servers. Also, I don't think too many players are left on the JP side.
Oh! They also censored the Joestar Mansion Dramatic Finish for NA. Instead of showing the spear going up someone's butt, it just whites out as they fall on it. Lame.