number six,
I still think the 5D is more accurate but only by a hair. However all photos were taken at 40mm and on the 5D that includes more of the wall in the photo then 40mm on the 40D (40mm on 40D is like 64mm). This might also be the reason for the 40D being a bit darker, because same f/stop and shutter were used on all photos.
After all it was just a quick test 
Oh....


