I've had the pleasure of working for and owning both Canon and Nikon Cameras. I would say its all down to preference, and mine, for professional photography, it has to be Nikon. But thats because I prefer how the AF works, I prefer the algorithms that the sensor uses.
You can see this demonstrated at http://www.oskarbi.co.uk
try it soon as it will soon be updated as the domain name for a friend's quality management traning company.