This purely personal. I tried both cameras and they essentially are superb cameras. Ultimately, you want to invest in lenses. But, here is my 2 cents…

My reasons for a D70:
a) the fit, feel of the camera for me is better. It seems more durable and heavier… feels like a pro camera

b) My roommate already owns a Nikon D100. Both groups (nikon and canon) have a strong following. It just happened that the people around me are more familiar with a Nikon D70. I have other friends who are D70 users.

c) I got into a sales talk and was convinced by checking out several stores that Nikon is pretty good.

Like what I said before, both cameras are excellent. I suggest you go to flickr and look for a discussion thread under FlickrCentral (under my name) since I essentially asked the same question to a host of pros.