I would go with the DSLite unless you really can't afford the extra $20.
You get a brighter screen, and better battery life in a more compact form
price comparison
http://www.ebgames.com/browse/search.aspx?N=0&Ntk=TitleKeyword&Ntx=mode+matchallpartial&Ntt=ds
Note: Normally I would suggest you use the VGChartz amazon store (as you can get it like $5 cheaper), but I don't trust buying used hardware off of e-bay/amazon