No it's based on various other sources. Achievable performance is in the PS3's advantage, the difficulty in writing / porting software is in the XBox 360's advantage.
Although I prefer everything on one disc I am not afraid, it's the developers who make sacrifices. For instance on the PS3 for Motorstorm and Resistance uncompressed 7.1 audio support was included, because there wasn't a need to offer anything less than the best the industry is offering today (other exclusive games like Lair will support this as well). I don't think we will see 7.1 audio in major XBox 360 Elite games, the added cost of additional discs is not worth satisfying a minorty of people having the audio sets to enoy 7.1 Audio and the HDMI port included is half the bandwidth of the one found with the PS3, which I believe will be an advantage later on when games need to push more data like 48-bit deep color 1080p graphics in combination with 7.1 Audio.
Would people have preferred God of War 2 for the PS2 to be supplied on many CDs or just one DVD? In the past the PS2 was heavily criticized by many people for going with DVD instead of using just CDs, but I think that was an equally wise decision as going with Blu-Ray now, at least if having an eye on the long term future
