Originally Posted by
bobones
Because you pedal with the balls of your feet, not your heels.
+1
OP...try both and see what works for you. Both are high for me. Not only does how you measure your cycling inseam method aka thin book method...but also seat shape and width and how you pedal...toe down versus normal and how long your feet are and where you mount your cleats and what your cleat stack height is. Also depends on your hip flexibility. Since I am older with less flexibility than a pro and ride with my cleats more rearward which shortens my effective foot length, I ride with my saddle a bit lower than what my inseam measures per either method.
Hope that helps.