Generally they are 2 subspecies of Geochelone pardalis. They are found in different regions in Africa.
Pardalis pardalis are larger and harder to find. They have 2 dots on their plastron as opposed to Babcocki that are smaller and have 1 dot. Lots of hybrids out there that will kind of give variation on size, that being said, Pardalis pardalis should be bred to pure Pardalis pardalis and not to babcocki.