If this were 3 years ago I'd say go with the Canon without even having to think about it. But, it's not 3 years ago anymore. ;) Canon use to be the king of the Digital SLR world, but everyone is catching up, unless you are interested in higher end D-SLR's like the EOS-1Ds Mark III.
Just go with what camera offers the features you like or want and which can provide quality accessories at the right price. Either the Nikon or Canon will be a great camera.