As regards dropping camera equipment on hard surfaces, I should add although I'm still using my Sigma 15-30 several years later, after dropping it in the rainforest whilst changing lenses, I had to send the lens in for repair recently because the diaphragm got stuck wide open, resulting in serious everexposure at F16. This was a fault which developed gradually. The first indication that something was wrong became apparent when auto-bracketing exposures in TV mode. Mysteriously, all shots would have equal exposure at different apertures.
The point I'm making is, although a camera might appear to be functioning well immediately after an accident, the less robust camera might be weakened in such a way that a fault appears some time later, perhaps years later, that is directly related to that accident.
One might dunk both the 5D2 and 1Ds3 in water for the same period of time and find that both cameras appear to work perfectly well afterwards. However, it might be the case that the 5D2 lets in a tiny amount of water around the shutter button (for example) that has no immediate effect on the camera's performance, but causes some slight corrosion before it dries. That weakened component, due to corrosion, might malfunction years down the track, or perhaps only months later.
