Here's the article I was talking about, back last year when they decided to take Assassin's Creed to multiplatform, rather than stay exclusive to the PS3:
"While the PlayStation 3 and 360 versions of Assassin's Creed are virtually identical, Raymond did say that on the 360 the team is putting a special emphasis on achievements. The hardware also allows for improved threading, which will improve even further the crowd AI."
http://pc.ign.com/articles/736/736396p1.html
I have no problem believing this, simply because of the difficulty many 3rd party devs have been experiencing when programming on the Cell. There have been delays on multiplatform releases for the PS3 (Stranglehold, GRAW2), as well as day-and-date releases that are inferior to the 360 counterpart (Madden 08, NCAA Football 08). Programming for the Cell is still in its infancy for dev teams that don't want to sink 20+ million into a game that might not sell as well as it could on the 360.
Threads of Interest:
The Movie Thread: http://www.vgchartz.com/forum/thread.php?id=6880
The Crow Eating Thread: http://www.vgchartz.com/forum/thread.php?start=0&id=3886
The Betting Thread: http://www.vgchartz.com/forum/thread.php?start=0&id=7104
Custom GIFs Thread: http://www.vgchartz.com/forum/thread.php?id=18963
The Greatest Game Ever Conceived On Any Platform
Tag: "I have tasted Obi-Wan's bitter tears"