I have a Canon D10. Very happy with it. It's advantage over the Olympus's I've toyed with is time. It powers up, snaps a picture, saves, and powers down much quicker. Picture quality is similar. A touch better out of the water, IMO. Perhaps a touch worse under water.
Disadvantage was cost and shape. It was more expensive than the others, and it's a weird round egg shape that doesn't fit well in pockets.
That said, Olympus has newer models I haven't toyed with. Canon has a new model too. And a billion other companies have entered the waterproof camera fray, I'm not up on all of them. Nikon has always been quality, and they have a waterproof now too.