Canon 30D versus the Nikon D200

Well, I've seen the shots from these two cameras and handled
them both. For noise, the Canon wins, having less noise but the
noise is more chromatic. The Nikon has more noise (this was a 1600
ISO) it is "monochromatic" and really gets bad with under exposure.
Shots underexposing human flesh should be avoided at all costs.
A noise program is going to have more trouble dealing with the Nikon
noise and will likely destroy more fine detail when removing it than
when removing noise from the Canon. The so-called "granular" or
film-like grainy noise is not desirable, owing to the difficulty of
removing it from images. The colourful blotchy noise is easy to deal
with. The noise differences between the cameras at correct exposure
are not radically different but the differences are there.

As for the cameras themselves, the D200 wins. One noticeable thing,
the shutter/mirror slap in the Canon is much harsher, a real clunk is
felt when it fires. Both are harsher than Olympus's E-1, which makes
sense probably because of the larger (heavier) mirrors/mechanisms.

In fact with high end glass, ( used L on the Canon) they are both
heavy cameras with basic "normal" (17-40 or so) zoom lenses attached.
This will actually help mitigate any vibration caused by Canon's rough
firing.

Here's a Canon image, 17-40L 1600 ISO taken in a store.
Noise is well supressed.

http://www.pbase.com/andersonrm/image/57631694