Wow, tough choice and I can't help. Here are my thoughts though...
My "peeps" (read resources" have always said the white machine itself is better made than the black although the case itself is of poorer quality.
The white ones almost always go for a higher price while the black ones are still occasionally found for a song. If you get the white one you may still pick up a cheap black one later on down the road. If you get the black one, not so likely you'll get a cheap white one later on.
The black one is a Centennial model and hence generally goes for a little more and it is in somewhat better shape than the white one.
Wish my brother would give me a tan FW. He won't even give me the time of day so that is not likely to happen though.