Everyone's Lite-happy these days, but the original DS is a great workhorse handheld and better value than ever. If you can cope with the bigger size and clunky looks, you'll find it has several advantages over its little brother.
First, it's clunky because it's well-made -- build quality is significantly higher than the Lite. Second, the bigger size allows a slightly but noticeably better sound/speaker system. Third, the size also means that if you play GBA games on your DS, the carts fit flush to the console, rather than sticking out as they do in the Lite. That mightn't sound like much, but it means you can leave a GBA cart in without worrying about it catching on something in your bag/pocket and damaging your DS.
Finally, some have complained about the D-pad on the DS Lite, claiming that it's harder to find the diagonal positions. I think that may be correct; but given that stylus control is likely to be the better option with most games that feature 8-way movement, it's unlikely to be a major issue.
It's not all good news, of course. Most importantly, the original screens look dingy compared to the Lite's stunning displays. Out-of-doors play is virtually impossible on the older console. The Lite's chubby stylus, side-mounted power switch and general aesthetic improvements also make it very desirable.
Still, you get a strap and spare stylus with the old DS, compared to no accessories whatsoever with the Lite. You also get to play exactly the same extraordinary games, on a console that will probably last longer than its sexier-looking sibling. The choice is yours -- just don't dismiss the original DS out of hand.