practical comparison plane spotting 40d-50d
Surprisingly the different exposure correction values I put in - from plus 1/3 to + 2/3 - had very little effect on images which makes me feel that both cameras have a very reliable exposure meter producing good results already at standard setting
Hmm, there's a flaw in your logic. If the exposure meter was giving the correct exposure at +/-0, then the image should have been slightly over exposed at +1/3 and +2/3. What you results really say is that under your viewing conditions, the images had at least a 2/3 stop exposure tolerance. Someone else may look at your unprocessed RAW files and say that the +/-0 was best, OR they may say that the +2/3 was best and you should have gone to at least +1.5 for the optimal shot.
I often shoot with both a 7D and a 40D (in fact, I did last night). With well exposed images at ISOs of roughly 100 to 800, without significant cropping, the two can take comparable images. But the 7D has many advantages otherwise (such as more focusing spots and switching the focus point from vertical to horizontal when the camera is rotated - both features I missed on the 40D last night).