Yes - the white balance - underwater' setting alone sounds so much easier than the Canon S90 and
S95 one-click white balance button.
If you are likely to want to keep things simple, the Canon produces nice photos.
If you are like me and are likely to want to experiement with more and more additions - probably
it's the Olympus.
After some use, with a 'deep' homemade LCD viewing shade, the screen and all the details can
be seen, can see the fish, can see the focus. Lovely. (Even better with the LCD viewer/ loupe.)
The Olympus XZ-1 works very well indeed. So well, I have bought another for my wife.
I saw no need for the later XZ-2. The tilting, touch screen can't be used when in a housing and
it is more expensive than the XZ-1.