I don’t want to start a big fight here, but does anyone have any proof that practicing with wood produces a superior hitter than if metal was used for practice? In the pre-BBCOR days, even I was pro wood for practice, but being in Ca and having seen BBCOR in HS since it became mandatory in college, I no longer feel that way because I see no significant bump in performance with BBCOR over wood.
BBCOR swings lighter than wood. That's a scientific fact. The MOI limits on BBCOR bats are designed to allow this. So if you believe in slight overload training, then you believe in training with wood.
More important, BBCOR (because it's an engineered hollow tube) is more forgiving on hits away from the sweetspot. I don't need a scientist to tell me that training with wood forces a hitter to work harder--and get better--at getting the sweetspot to the ball.
And, there's the mental boost that comes from using a superior bat (metal) in games after having hit the ball consistently and hard with an inferior bat (wood) in practice.