Re: Blu-Ray wth???
The codec(s) used is decided by the studio. It's weird, though, that a number of movies that have come out in both formats have been done in VC-1 for HD DVD and MPEG-2 for BD. It seems to me that if you've already done VC-1 for HD DVD, it would make sense to just use that on the BD as well, saving space and allowing for more content on the BD release.
Have yet to see that, though.