Really? From the way it looks, ds looks bigger than the gba(bottom half looks gba sized + some, and top half looks like half a gba + some), whereas the dimensions of psp are smaller than the original gba is everyway except length.(so overall it's bigger)
From the comparison pic I saw the DS is the same length as the original GBA. When its folded its the same length and height as an original GBA but a bit thicker.