The XD card is somewhat of a drawback but Olympus owns it so that's why they use it. The 1 GIG card comes in high speed but the 2 GIG does not.
Before you decide on either of these cameras I strongly suggest you look at the newer SP550UZ. The 18X zoom may not be of much use underwater but I believe the lens on this model is the widest yet for an Olympus point-n-shoot. It also has RAW. The Ike housing won't be out till June.
Another thing I noticed when handling this camera is the zoom feature works in the macro mode. Most of the newer other brand point-n-shoot cameras do not. You have to move the entire camera to and from the subject.
You can also turn the flash off even though it is in the up position. Some other brands, such as the Fuji E900, won't allow you to take a non-flash shot without first closing the pop-up flash.
The SP550UZ would be my choice in a point-n-shoot camera and likely will be my upgrade.