In a recent interview, Voliton's Rick White claimed that their latest title, Red Faction: Guerilla, has maxed the 360.  He explains that the developer had trouble striking a balance between the amount of polygons the game pushed.

Marketing intentions aside, what's interesting is that, from what he's saying, it doesn't sound like a problem the PS3 version would have.  The 360's unified GPU has to balance the amount of polygons it can push versus it's the amount of pixels it can push.  If you push more polygons, than you have ease up on the amount of pixels you push, and vice versa.  Where as the PS3 doesn't have that problem, it's GPU isn't unified.  While the PS3 can't push high numbers of polys as well as the 360's GPU, in a game like this, where the poly count is low, the pixel count is unaffected.  This doesn't create the problem of having to balance the two.

This isn't to say the PS3 is better than the 360 by any means - the gripes of numerous developers would testify otherwise.  Rather, in this specific instance, the PS3 is better designed to handle this type of game.  Of course, we also aren't members of the development team, so this is purely speculation.