I was more hoping for a low-light suit picture, brightened in post for comparison, but Canon bashing is good too.
I did see a ISO 25600 comparison image taken with 5DmkIII and D800, in the same controlled test setup, full-sized jpegs. The entire ISO series was there, but I only checked the one high ISO. I found a test tool where you can see this yourself here, looking at the still-life set of shots at the bottom. Also, looking again, I'm not sure how controlled the test setup is. The lighting appears to be different. A different shade, and shadows moved. Still, from what I can see, the 5D looks significantly less noisy at 100%, which is expected due to the lower pixel count. However the Nikon noise is fairly severe. Straight edges didn't look quite straight anymore, with lots of splotchyness. See the crayons, and the edges of the color palette squares. It looks like the Nikon would require more post work. I'd rather have the Canon.
Still, both blow away my T1i, and I could gratefully accept either one as a gift.![]()