Where my dd trains at they use exit speed off a tee,they did measure her bat speed one time , but since then only exit speed of the ball off a tee.She hit 63.2 mph at 12yo at the time but avg. is 61.1.So I have to ask this which one has more benifit? IMO,I believe neither one matters, a girl can get all sorts of high #'s,but if they have bad mech. or cant hit live pitching it doesnt really matter.