It seems that some have forgotten that the original use of the letter S by both Canon and Nikon was to represent S(tudio). Therefore a D3s has a different purpose (from the manufacturers point of view) to a D3. And Studio work at a Pro level needs lots of pixels and less need for high ISO.
Comparing an S designated body against its non S equivalent, for both Canon and Nikon is rather an exercise in futility. The fact that people are using the D3s for sports/landscapes etc is a testament to its quality, but it is primarily a studio camera, and therefore high ISO is not an important factor for the manufacturer.