I have both the G11 and S90 canons and if i were to do it over i would probably go the S90/95 route as the camera is so easy to carry in a pocket top side - the g series is a brick in your pocket. If you don't have the camera with you, you can't take the photo. However I would miss using the g11 for topside macro as the S just can't get close enough but things even out underwater with wet lenses.
Then I will buy the s90 today