In his first post on the official PlayStation Blog, Seth Luisi, director of development at SCEA talked about one of the games he is currently working on, namely SOCOM: U.S. Navy SEALs Confrontation. In particular, Seth said that the game is "not possible" on any other gaming console, largely due to its aggressive use of the Hard Disc Drive that comes with every PS3 model.
He's right, in a way. Wii doesn't have a hard drive (yet, at least) and Xbox 360 doesn't come standard with a hard drive, unless you buy the Premium or Elite package. So if your game is going to rely on a hard drive to stream data, PS3 is the best choice.
Inside the Developers Studio: Seth Luisi [PlayStation.Blog]