I own neither, but I'd definitely go with Black.
I remember my sister getting a white iBook in 2001 and 2002. Back then they were so "hip" because everyone was either using a Thinkpad or a Charcoal Grey Dell.
Now, laptops look much more sleek and white MacBooks look like toys. The only time when they look OK is in a picture.
I recall going to the Apple store a couple of weeks ago pondering if I wanted to buy a MacBook Pro or a black MacBook. At the store, everyone was fixed around the black MacBooks and the White ones were unoccupied, and it was easy to see why. They looked cool and different then, but now they look like the "old" Apple.
I'm an elitist prick, so I like people to notice that I'm using an Apple computer. One concern in this thread is that black MacBooks look like Dells, because Dell has recently started putting white Apple logos on the front of their laptops.
It's obvious to see that they're Mac, and they really look like the new Apple, aluminum and black -- which really look much more sleek than White MacBooks.
The fact that you're even asking us tells me that you have the money to spend for either. Personally, when making a $1300 purchase a hundred or two dollars is something to consider, especially since you'll be using it for years.
People say you're only paying for the color, but you're paying for an extra 90GB of space and better material. Cracks or fingerprints. Oh, wait. The new Penryn MacBooks came with new material which made them more resistant to fingerprints!
In the end, only you can make the choice. I can afford a white MacBook now, but I'm saving for a black one.
