This is our standard studio scene comparison shot taken from exactly the same tripod position. Lighting: daylight simulation, >98% CRI. Crops are 100%. Ambient temperature was approximately 22°C (~72°F). Camera settings as per previous pages.
Canon EOS-1DS Mark III (RAW) vs. Nikon D3 (RAW)
Canon EOS-1Ds Mark III (RAW)
Nikon D3 (RAW)
4.8 MB JPEG (5616 x 3744)
3.3 MB JPEG (4256 x 2382)
Shooting RAW and equalizing the amount of software sharpening to the output of the D3 and 1DS Mark III produces no surprises; the cameras would appear to be very similar indeed in terms of per-pixel sharpness and obviously have a similar strength AA filter. So the difference (at base ISO) comes down to how much resolution you need; the 1-DS Mark III's 1000 pixel or so advantage in both horizontal and vertical directions (912 vertically by 1360 horizontally to be precise) means more resolution and more fine detail and the ability to produce larger prints or crop more aggressively. Of course whether you actually need that much resolution is another matter altogether, and will vary from photographer to photographer.