Well... Say you're at -7 after an attack. Since Hitomi's parry is immediate, you can parry the fastest punches in the game, but since Leifang's requires 6 startup frames, you can get hit by any punch that's 11i or faster before she starts actually parrying. It's the difference between getting hit while receiving damage, or actually parrying and dealing small damage. That is an advantage. Although, I admit it's a small one, and the advantage of the follow-ups of Leifang's gives much greater benefits overall. Despite them having the same function, the parries are to be used in a slightly different way. You have to be slightly more careful in throwing out the parry with Leifang since you will get hit if you don't use it at the right times.