Like most multi-console games, any review would inevitably have to come down to which system is better, and for this instance, the PS3 winds up winning out just slightly. It's not in the gameplay department, because DMC4 plays the same regardless of which system that you play on. Nor is it in the visual department, because visual issues are virtually negligible. For example, the 360 has some harder edges to some characters during cutscenes, and a little more screen tearing than the PS3 at times. The PS3 can be a wee bit darker during some scenes, though. Both systems show off a certain amount of render passing that pops into focus on sweeping vista shots, but they occur at the same time on each system and are quickly dismissed. However, observing these differences will only come via frame-by-frame analysis of each game side-by-side. Even then, you're still receiving an incredible visual experience.
No, the edge comes in the fact that the PS3 installs a large amount of game files to the hard drive, dramatically reducing load times between stages and cinematics. I've timed the game on both systems numerous times, and each time has been consistently in the PS3's favor. Transitions to gameplay from starting menus are relatively close, frequently within half a second or so of each other, but when you're loading up a cutscene or having another pause in the action, the 360's times are easily three times that of the PS3.