Using two letters does have the advantage of distinguishing between kana that sound the same like じ/ぢ and ず/づ. While the former set can be pronounced either /ʒi/ or /dʒi/ and the second set can be pronounced either /zu/ or /dzu/ in free variation, there is no difference between the two kana in those same sets.
Using two letters does have
Using two letters does have the advantage of distinguishing between kana that sound the same like じ/ぢ and ず/づ. While the former set can be pronounced either /ʒi/ or /dʒi/ and the second set can be pronounced either /zu/ or /dzu/ in free variation, there is no difference between the two kana in those same sets.