I just don't see how the 360 version can be the same.
Why? Because in an interview with Itagaki from 2005 that I've pointed out on this site before, he says his team was really knocked out when they discovered the 360 was going to be using dvd as its main disc type (Itakagi thought that it was going to be using HD-DVDs). He further said in this interview that he wanted the bigger disc space because it would let him put more cutscenes that would appeal to Japanese gamers in his games and he said that to put even the two minute High-Definition trailer for DoA 4 from E3 on the 360's dvds in a quality that was acceptable to him that that would take 2 gigs of the discs 9 gig space leaving him far less room than he considered adequate for other parts of the game.
Now, presuming that what Itagaki thinks is a suitable quality for high definition cinemas is roughly the same thing as what Square thinks it is, then you probably have 45 to 60 minutes of hd cinemas in Final Fantasy XIII which according to Itagaki's standards would make the cinemas in FFXIII have to be around 50 gig in size. Let's say the rest of the game only takes up about 10 gigs of space, then you have FFXIII taking up 60 gigs of disc space and close to seven dvd 9s to be at the same quality
So, I really don't know how the two games can be anywhere near identical when you take into consideration what Itagaki said would be the required space to get his two minute cinema at the quality that he wanted it to be in on a dvd 9 when there will probably be 50 minutes of cinema in FFXIII.
EDIT: Although I do think I see a way around this. It could be that the plan is for gamers to use the 360's hard drive feature that was into the new xbox dashboard where you can save games off of the disc to your 360's hard drive to compensate for the dvd's lack of space, but do you really want to be taking up 45 to 60 gigs of space on the 360's hard drive to play FFXIII?
Heavens to Murgatoids.