the ps3 dev kit would have been finalized earlier or 360 later
blu ray would have been dropped for ps3 or hd dvd likely added to 360
the cell wouldnt have been ready for ps3 or 360 would have had a well designed machine.
ps3 costs would have been even higher (or a completely different machine) or 360 costs lower (or a different machine).
i think it would have most benefited ps3, but too many intangibles.