I think the saying was "there are many paths at the base of the mountain but the all lead to the top".
"A hunter who chases two rabbits will catch neither."
I am pretty sure there is only one rabbit because it is really hard to find a unique martial art. What I am trying to say is that martial arts share so many techniques the only thing that seperates them is the martial artist and how she/he is taught to use the art.
I like to think martial arts as martial stategies. An aikidoist uses absolute defence to ensure the effectiveness of the art. Any attempt to be aggressive may expose weaknesses in the array of martial techniques used in aikido.