I got the black bezel for the iPad (only choice was black) and then black again for the iPad 2, but I'm going with white for the new iPad because:
1) As weird as this may sound, white blends in better with the environment and the screen when the background displayed on the screen is white. Or in general, it makes reading much easier as there isn't a stark contrast between the screen and the bezel.
2) it makes black more like black and less like dark gray. This was a problem with the iPad and iPad 2 because I could easily see that the screen was brighter than the bezel with a black background.
3) Light leak is less annoying on white.
4) In the dark, regardless of whether the bezel is black or white, it blends in anyway, so you'll still be able to enjoy movies and photos.
5) As mentioned, white reflects light, so it doesn't heat up as bad as black, and it doesn't reflect my reflection so it's less annoying under direct sunlight.