Well, there are a couple of other threads here with active discussions on why one body was chosen over the other. Rather than add to the noise I thought I would link this video. This was a MAJOR reason I went to the Olympus system. I'm still learning some of the best settings, etc. but I will get there. http://youtu.be/N9Omqui0SoI I'm not totally sure my 1Dxx system could withstand this amount of water. I am pretty confident with the body, but I would never subject any Canon lens to this. I am pretty confident it would fail. My sealed lenses do just fine in downpours I've experienced in places like SE Asia, but this Olympus system is (At least) partially submerged! The Canon lenses also -require- a filter to complete the water resistance, the Olympus 12-40 pro does not.