Maple is a very hard, dense wood. The surface hardness is about 20% greater than ash.
Ash on the other hand does flex. When a ball is hit with an ash bat, there is a trampoline effect
Bamboo is also a newer choice on the market. Many companies have recently introduced bamboo models
Birch is tougher than ash, and more flexible than maple. This hard hitting imported wood does not flake like ash and out-performs maple.
But i think that composite wood bats are best as they are typically some combination of different wood types that have been fused together to make a more durable bat. For this reason composite bats will last the longest, and will also be among the most expensive wood bats.
Thanks for taking a look.