What Nintendo DS would you by?
I would buy a Nintendo DS. They are cheaper, and more games are available. The only real difference is that the DS doesn't take pictures.
Yes, PokÃ©mon LeafGreen will work on a Nintendo DS system as long as it's the original Nintendo DS system that is referred to as the Nintendo DS Phat and the Nintendo DS Lite. The Nintendo DSi, Nintendo DSi XL, the Nintendo 3DS and the Nintendo 3DS XL cannot play LeafGreen because they do not have the Gameboy slot like the originial DS and the DS Lite do.