Maple bats are extremely hard and dense and therefore aid the ball in jumping off the bat faster than any other type of wood.
The surface itself is approximately 20% harder and has a closer grain than ash. The hardness of maple makes it the least flexible.
Ash is much more flexible than maple and has a "trampoline" effect when it is struck by the ball. Instead of jumping off of the bat like maple, ash bats have a
spring-board effect and absorb contact with the ball. Ash bats usually have a larger "sweet spot" which gives them a bigger area to make solid contact.
Birch is a tougher wood than ash and is also much more flexible than maple. Birch is also a much lighter wood than both ash and maple,
which allows hitters faster bat speed.