I have noticed that if you install all of your discs on the 360 version, it does gain (slightly) faster load times than its PS3 counterpart. Of course, that means you'll have to sacrifice nearly 18GB of space on your hard drive for marginally improved loading... personally, I can stand to wait the extra quarter of a second...

...but my roommate got the FFXIII bundle with the 250GB hard drive, so why not?