That is fantastic advice for any beginner up to someone relatively advanced. At the professional end it does make a difference, recent high-end Nikons have been

That is fantastic advice for any beginner up to someone relatively advanced. At the professional end it does make a difference, recent high-end Nikons have been truly excellent cameras and have had much better noise reduction and autofocus than the Canons. It still makes much less difference than the skill of the photographer, though. It's like Windows/Mac, Emacs/Vim etc etc - they each have their advantages that will probably only matter to a very small percentage of users.