With regards to ps3 versions of game selling better than 360's, I argue that it's the exception not the norm. points of interest, on this site alone, 2 multies are in the top 10 Darksiders and COD:MW2 the 360 version of both games are doing better than the ps3's.
I agree the ps3 version of ff13 will do better, but I argue that no matter how much it sells, do you really think that will be enough for SE?
Goes back to my arguement of less effort+more returns=win.
If this was a 360 exclusive originally, I argue E3 '08 would not have happened in Sony's direction why?
1: too much work to port
2: Not garunteed to be successful if past trends are to be believed.
3: (personal belief) for some reason, SE amongst others are more willing to please MS than Sony atm so the liklihood of ps3 ports being perfected to match the 360 counterpart is unlikely.