My iPhone was black. My iPhone (2nd gen.) was black. My iPhone 3g was black. My iPhone 3gs was black. My iPad 1 wifi was black. My iPad 1 wifi + 3g was white. My iPhone 4 was white. My iPhone 4S is white. My new iPad is white, and is currently sitting in Nashville, TN probably listening to some good music and drinking a beer at Tootsie's or the Wagon Wheel. I'm so jealous.
Seriously though... having had both colors I prefer the white. My white devices have never shown dirt or smudges any more or less than the black devices. Neither was better for reading, viewing videos, playing games, or using any other app. It all comes down to an aesthetic preference. Mine is white. I think it looks clean and hip. Apple's signature color is white. I don't know why, but white apple devices make me happy... they give me the warm and fuzzies. Isn't that all that really matters??
Have I mentioned that I'm ready to get my new iPad?!?!?!