It depends on how big the cornrows are. If they are narrow, the difference in length between their tails and my own hair is minimal. If they are thick/fat, it's a lot greater.
I would not expect braided hair to be the same length as non-braided hair coz unless we're talking about non-braided shrunken hair which would be like comparing apples to oranges, braided hair bends one way then another so it's basically hair that isn't stretched out straight but meandering. So it'd obviously fall a lot shorter.