the way I see it is...everyone knows games made by ID are texture whores and bluray being bigger is able to have more higher res textures since ID is too cheap to licence a 3 disk game for the 360 and is doing it on 2 disks.
I don't see gameplay being worse on the 360 because of this.
Also think of it this way...higher res textures + slow bluray = lots of load times for ps3.
Lets wait for reviews shall we...