another possibility is that you shot the duck at the full 12x zoom, with the camera in auto. In order for the camera to take the shot at full zoom, hand held, it had to ramp the ISO up itself – seems the max is 1600. see these two shots comparing iso 1600 with 100
The s95 has a much smaller telephoto effect at the long end of the zoom range, and I suspect the dog shot was at the more wide angle end of that range.. I suspect that shot was taken at a much lower ISO value.
So it’s not really the cameras fault the duck image looks nasty – i suspect you were just asking too much of it in the conditions. Had the S95 had the same lens on, the result would have as near as damnit identical
[edit] or had you taken the dog photo with the sx200 at the same zoom position in the same conditions, I reckon you’d have barely been able to tell the difference.