What DS do I buy? - She's 9- and really Tech savvy?

Dsi or 3ds. Do not bother with the XL it is the same thing but bigger and cost more. Also it ruins your vision. Ebay has cheap ones, make sure you mark it under new. And also take the sellers review 99 is good for rates.

3ds it has 3d games! :) unlike other people I'd say look into XL versions to choose for yourself, I'm sure your daughter would prefer the XL because its larger and most kids these days want bigger and better lol it does not hurt your eyes or damage vision although if you view 3D too long you could get dizzy, but you'd usually would have to have sensitive eyes. Anyways I recommend 3DS it's the latest model

3DS if you want her to buy the newer games and can still play the old games.

DSi if you're on a budget, but I don't recommend.

Don't bother with XL as they're just more expensive for a big console.

Get a 3DS. It can play regular DS games and 3DS games. It has really good quality as well

i believe the 3DS is the latest model.its pretty cool get that one.