If the game comes close to filling up a dual-layer Blu-ray, it would take at least 6 DVDs (more likely 7) to hold the same data at the same compression rates. You have to take into account the amount of sound, textures and code that HAS to be duplicated on every disc in order for the game to run.
Switching from uncompressed 7.1 audio in the PS3 version, should bring it down to 5-6 DVDs with minimal sound difference (you have to have a serious surround sound setup and an amazing ear to hear it). Of course having to decompress the sound files will take a small amount of additional processing power in the 360.
The cutscenes will most likely be compressed in H.264 or similar. They're not going to be able to squeeze much more out of them without dropping the quality or resolution, which I doubt they want to do.
The in-game graphics and framerates should be comparable. I've read a few interviews where developers have said porting a game from PS3 to 360 is easier than 360 to PS3 (which has caused the 30fps PS3 games).
And for those comparing FF13 to Lost Odyssey's 4 discs. Those two games are in completely different leagues. There hasn't been an FF-level RPG yet this generation.
Overall, it should have the same graphics, framerate and cut-scenes with a marginal drop in audio quality on the 360 on 5-6 DVDs. PS3 version will be the version to buy, if you have both consoles. But it won't be that big of a difference. I'm just tired of all this wasted development time on multi-plat releases. Everyone remembers that the Versus team was moved over to FF13 in order to get it finished right? So maybe this isn't delaying FF13 all that much, but it sure as hell is delaying Versus.







