Black gets fingerprints on it easily (the glossy parts), whereas white gets dirt and grime on it easily (the shoulder buttons)... If you plan to use a case for your DS, I'd say that white is definitely slicker looking. However, if you go without a case, your white DS will quickly look like crap. I had a white DS lite that I traded in because it got too dirty and uncleanable. I use a case now.
Both of my DS Lites are Black. My brthers is Black, and my Friends is Black...um...i'm starting to see a pattern.... My girlfriends original DS is Pink though ¬_¬