I would go with GBA.
The GBA just has more games that I go back to regularly. Kirby and the Amazing Mirror, Metroid Fusion/Zero Mission, Mega Man Zero, Mario and Luigi, Astro Boy, Golden Suns.
The DS doesn't have too many games I replay very often. Kirby Superstar Ultra, Bowser's Inside Story, and the Phoenix Wright games. Nothing else really comes to mind for me.
So GBA for me.







