Through the same amp , Cornford MK50II, 2 x 12 G12M Heritage Speakers, same medium overdrive and EQ, the Crawlers, to my ears, are more PAF sounding, whereas the Rebel Yells are fatter with more high end emphasis.
If you listen to the Top Gun Theme thats pretty much what the RB's sound like, when played through my rig anyway.
http://www.youtube.com/watch?v=zCTJmXrgsFg.
Awesome, I think this cements the RY as the right choice then. Someday I'll have to try out the Crawlers to though, been meaning to for a while now.