Erich- In immature plumage, these two species are relatively easy to separate but I have a lot of trouble with adults such as this. My hunch is that it's a small bird because we have the dove for comparison, so I would vote for a Sharpie.
Cooper's & Sharp-shinned are notoriously difficult at times to ID, especially when most of the relevant features are not visible.
However, if the prey here is a Collared Dove & the overall pale colouring certainly suggests that species, then we can assess the size of hawk from its victim. IMO it appears to be significantly larger. Details from Sibley's guide are:
Sharp-shinned Hawk 11" & 5 oz (140g);
Collared Dove 13" & 7 oz (200g);
Cooper's Hawk 16.5" & 1lb (450g).
Another pro-Cooper's feature (again from the Sibley guide) is the pale nape.
I agree with the observations made, but always find it hard to assess just from comparison with prey - after all the Dove is torn apart, so what was its original size? To me, on the hawk, the eye appears large, the head is rounded, and although there are 2 pale spots, the nape is not really pale - all features that would favor Sharpie over Coopers. But from this image alone, I'm not sure that it's possible to make a definitive ID.
Thanks for this very helpful link. There's no doubt in my mind now that the accipiter that attacked the dove in my backyard was a Cooper's. The color, proportions, and size of the hawk match exactly the description of the Cooper's, and not the sharp-shinned, in the Cornell article. Thanks again!