Well if it's like Oblivion, PS3 version will have slightly less smooth graphics but a slightly faster/farther rendering.
Oblivion was different from most multiplatform games. The PS3 version was actually all-around superior in the technical department (excluding the 2xAA of the 360 version) providing better texture filtering, a higher native resolution, a farther draw distance, faster rendering, and far shorter loading times, but it came out a year later and was programmed to be more than just some lousy port. Fallout 3, a game released simultaneously on all platforms and actually ported to the PS3 by Bethesda instead of another company they outsourced it to, may be a better indication of what Bethesda will do with Skyrim. The PS3 version of Fallout 3 had better texture-filtering and less screen-tearing while the 360 version had AA and less framerate drops (at the cost of more screen-tearing as V-sync was programmed to run off on the 360 version whenever it was needed to keep the framerate up with the PS3 version always has V-sync on at all times). I'm not sure if load times, draw distance, or rendering speed were different between the two versions, either, but the 360 version did end up getting DLC first and there was some major flaw with files swelling up on the PS3 version after it got its DLC in addition to certain overlooked oddities and glitches with the PS3 version of the DLC. So, while Bethesda did fine with the original Fallout 3, they really screwed something up with the DLC and never bothered to fix or acknowledge it. Regardless, I doubt that will happen again (although I can't comment on timed platform exclusivity).
Then again, perhaps the 360 version of Oblivion was similar in the way of having V-sync deactivate, sometimes, while the PS3 version just doesn't have any screen-tearing and by having some AA. I know, for sure, that the 360 version of Oblivion had 2xAA while the PS3 version had none, but I'm not sure about screen-tearing and V-sync aside from being able to say, from experience, that the PS3 version of Oblivion has very little screen-tearing... if any, at all. Regardless, Oblivion was undoubtedly superior on the PS3 while Fallout 3, likely being a 360 port, was more about equal with some strengths and weaknesses for both versions. Oblivion was most certainly a PC port, however (Some may cite the UI as proof as otherwise, but that's just a UI, not technical mechanics and Bethesda simply had no idea what the 360's final specs even were through the majority of Oblivion's development, so the 360 version of Oblivion was most certainly a PC port.)... to both the 360 and the PS3... but I can say that it was very well-done port on the PS3 side of things.