The buttons on the original DS console aren't that great. Try playing Mario Kart DS for a four hour multiplayer session and you'll see exactly what I mean. Last time I tried that one, I had an imprint of the 'A' button on my thumb for the next twelve hours. The pain was quite bad, actually. =/

The DS-Lite has much more comfortable controls, not to mention the nice, bright screen. *votes for the lite*