This is really OT, this BD/DVD/CD discussion, but why is it relevant? All of those storage mediums are weak, at best, at streaming data in real-time. Since its a technical requirement that no 360 game requires a HDD, or even benefits from anything other than a full install on the HDD, the PS3 has an advantage in this dept. A HDD for streaming is pretty handy, and reasonably fast. DVD.. no.
Any games which stream data off the 360 DVD are probably forced to require an install on the PS3 HDD due to speed issues, but conversely, DVD streaming is pathetic compared to HDD streaming. I imagine crossplatform devs rely upon DVD streaming as little as possible, for this reason. PS3 exclusives have the advantage of being able to use a HDD, and that's a big boon, if you need fast streaming.
In other words... who really cares about the transfer rates of any slow optical device, which is used only as a crutch when no faster method is available, due to lowest-common denominator technical requirements (like on the 360)?
