They both have a CIPA rating of 200 shots. DPR had this to say about the 95:
"Canon quotes a battery life of approximately 200 images per charge, but in our experience this represents the outer limit of the tiny 3.7Wh battery's abilities. In normal use we can squeeze between 150-200 images from the S95 before it gives up the ghost, which puts the camera firmly in the 'spare battery essential' category."
You can certainly fiddle with settings to coax the most life out of battery, but in my experience with various cameras, only by a +/- 10-20% factor. A number of advanced compacts will get twice this or more, but a couple spares are easy to carry so no big deal. It's a pain to have one go out when shooting on the go, however.