Nikon has traditionally had better glass than Canon. It's not really noticable, but when tested under lab conditions, the Nikon lenses were much sharper than the Canon lenses.
Of course, the difference is so miniscule that it's not too big a deal nowadays. And there's also the consideration of lens offerings... Canon with all their telephoto white-bodied lenses.
As for film camera bodies, I can't say which is better, but I do know that my Nikon F2 (from the mid-70s) has taken well over 10,000 photos and the shutter is still properly calibrated.