I think the depth of field issue is a draw. More depth of field can be good or bad depending on your intent. So perhaps it could be added to both lists as a notable difference. I am not sure what you mean by faster shutter speeds.
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Faster shutter speeds for the
same DoF. The 50D can be used at approximately 1 & 1/3rd stops wider aperture for the same DoF.
However, such an advantage is also associated with a disadvantage. If the wider apertures used are in the range of optimal lens sharpness, say F4 to F8 (or in the range dominated by diffraction), then the faster shutter speeds allowed are pure advantage.
When shallow DoF is sought and one uses say the 50/1.4 at F1.4, as opposed to F2.25 with full frame, then any advantage due to the faster shutter speed has to be offset against the softer image that the 50/1.4 inevitably produces at full aperture.
This problem is compounded by the fact that the higher density of the 50D sensor actually requires a
sharper lens in order to deliver image resolution on a par with that of the full frame sensor of similar pixel count, so in a sense there's a double whammy in this situation.
However, matters balance out when extensive DoF is sought. A lens at F10 should be sharper than the same lens at F16. And generally a lens at F7.1 should be sharper than the same lens at F11.
Edit: To add further complication, whilst it's true that at large f numbers the cropped format will have a shutter speed advantage which is not offset by lower lens resolution, the larger format, as a result of its larger light-gathering capacity, will tend to produces
less noise at high ISOs (comparing equal scenes with same DoF but different focal lengths).
The fact that one might be able increase ISO on the larger format, in order to achieve the same shutter speed as the cropped format at equivalent DoF,
without pushing noise beyond the level that exists on the cropped format at a lower ISO, sort of canels out that shutter speed advantage.
Not sure if it completely cancels out the shutter speed advantage. One would have to do careful comparisons with both cameras to be sure. At this stage, it seems likely I'll be getting both cameras. The 50D has the advantage of a faster frame rate, compared with the 5D2, and the advantage of micro-adjustment of lens auto-focussing characteristics, compared with the 40D. It should also prove to be at least a marginally better lens extender than the 40D as well as a few other bells and whistles.
