I cannot tell you which one better meets your needs, but I can say for me, the SX40 is on my list way before the S95. In fact I just got one for my sister for Christmas, and now I'm tempted to keep it myself.
Personally, most anything that I take with a non-SLR I figure is a compromise, and I like "up-close-and-personal" images which you have to literally be with the S95's limited zoom and are therefore more easily achieved with the SX40. And for the always have it with you size factor, cell phone images are better than none at all.
So the questions you have to ask yourself are what kind of shots do you intend to use it for, and how important is size?
Best of luck in your decision!