The two you list in your title are the most popular in this area. They have a different "look and feel" than each other, so this tends to be the final deciding factor for the end buyer. The specs are basically the same for waterproofing, with the Olympus coming out on top for shock tests.
Play with both and make a decision based on handling... At least that's my recommendation.
(I have an older Pentax w10 and it's been fine for basic couple feet of water, splash, surf type use)
And someone else was just asking about this, so try to search the forum as well..