I'm not so sure you need an underwater camera. Are you actually wanting to take it underwater, or are you just afraid that some splashing will ruin a regular camera? I don't own a rugged camera, but I've used my decade old digital camera in wet conditions including rain. Mind you, I try to keep it dry, and when it does get wet, I wipe it down immediately; I don't wait for water to seep in.
IMO your main concern should be the camera's performance (especially in low light), and then how rugged it is. A rugged camera would be of no use if it takes lousy low light images. But if you still want one, of the two I would go with the AW100. I've read the Sony's touchscreen doesn't work underwater, and I've also read reports of the sliding cover getting fouled from sand and debris.