dpreview.com did a
group test that includes the 2011 versions (might be slight lower in the model line as well?) of all three cameras you people are looking at and some other comparables.
Spoiler: Canon and Nikon won.
Be aware that they said the Canon autofocus is slow - if you're buying for the Olympics, you might want to weight that higher than they did. Another disclaimer: while camera models generally improve over time, sometimes designers make bad trade-offs in "upgrades" or one model improves enough to surpass another, so consider that as well.