The previews review of Assassin's Creed by IGN had the following statement.
"These big open worlds, which are fully interactive, do come at a severe cost on PS3. There is considerable texture pop-in and noticeable framerate issues. Playing back-to-back with the 360 version, it's obvious that Ubisoft did not devote enough resources to the PS3 edition. The framerate is considerably worse, so much so that it begins to affect gameplay in the later levels."
The full paragraph has been removed by IGN, though they are still keeping the final verdict and score unchanged.