I guess most of this specualation (which I think some is true) of the PS3 version of FF XIII being downgraded is because of the fact that M$ bought probably one of the biggest money-maker PS3 exclusives and got it for their system. I'm not 100% mad ad MS for getting the game but because of the fact that since they got it while it was about 40%-60% made for the PS3, they had to practically restart on making for the 360, it pre-longed the release date which I'm not 100% sure was suppossed to be a worldwide release date.
I'm no expert and CGI but when I played SO4, Last Remnant and Infinite Undiscovery, most of the cutscenes we used with gameplay graphics, and a big game like Final Fantasy XIII should be loaded with CGI cutscenes(in my opinion) I mean X, VII:DoC and XII had a good amount.
I just don't to see S-E developing games below their standard, which I think are very high since they were one of the pioneers of using CGI and the whole JRPG movement. and a game with the Final Fantasy title should be nothing but top-of-the-notch.