While you're all waiting to get your new iPad's (I am too!), you might be struggling with the idea of what color to get. Contrary to what you might think, it's not just personal preference. There are real functional differences between the two.
Let's draw analogues to other consumer products.
First, TV's. You may note that with very few exceptions, all TV bezels are done in black/dark grey/steel tones. Interesting, no? The reason for this is that a bright colored bezel will distract the eye and make the viewer acutely aware of the edge of the screen at all times. It's slightly more immersive to have a black bezel, which allows the edge of the screen to dissolve into the frame in many cases.
Second, cars. If you are a car person, you know that the reputation of black cars is one of requiring high maintenance to keep looking pristine. Dust and fingerprints contrast heavily with a shiny black frame. On a white iPad, this kind of dirtiness is hardly noticeable on the frame, although the screen itself may still present temporary uncleanliness.
Last, I've heard it claimed that the white iPad is a little less prone to overheat in sunlight due to the heat reflectiveness of the bezel. I'm not sure if this is true enough to an extent that it is noticeable, but, hey, why not mention it?
In the end, of course, what probably matters most is that you pick the color you feel more emotionally connected with. But it's fun to note that even tiny choices like color have real physical implications upon the way you use a product like the iPad.