Nikon Vs Canon; any suggestions?

A DSLR from any of the major brands will perform well and produce great images. Nikon, Canon, Olympus, Leica, Pentax, Sony all produce quality DSLR's. Professionals tend to be one brand people since they can use the old lenses when they upgrade camera bodies. If you already have a preference, get to a store and handle some cameras. There is no single best camera or camera that all professionals use. Look at some reviews at dpreview.com to help you out.