I don't have the catalog in front of me, but aren't they all the same? If I remember correctly, one of the four (?) different "meat birds" they sell just takes a little longer to mature.
I seriously read into it that after a while some of the breeding programs loose their ability to produce a fast bird (vigor??) and they are kept for a while to produce a "slower growing" bird.
I could be wrong, but they all look and sound like Cornish X's to me. (just my 2c)