It's funny how much kids are like adults when it comes to their sports equipment. In the same way adults have to have the latest and greatest golf club to get those extra few yards, and or straighten out that slice, kids too focus a lot on their equipment to improve their game.
I have no doubt that there is a difference amongst bats. I also have no doubt that bat speed and swing mechanics play a bigger role in the hitting of the ball than the composition of the bat.
All too often I see kids with bats much too long and much too heavy for their size and weight. Easton does a solid job with their recommendations for bat length and weight based upon the size of the player. check out their site for the fit chart. Additionally I have found a simple way to confirm bat size - have the player hold the bat our straight to the side or in front for a count of 10. If they can do this with no strain then chances are you have a proper fit. Once you leave the store you may have just bought the wrong bat without this handy test.
The real value in a good bat is the ability to drive bat speed, so if the bat is too heavy or too long bat speed will suffer. Slow bat speed equals poor hitting.
There is certainly something to be said for composite bats and the extra distance they can provide when bat speed is optimal. Note that these bats need several hundred hits for the sweet-spot to be developed so it is a really good idea if you are going to invest the big dollars in a composite bat to also invest the time to break it in... not to mention invest the time in developing optimal swing mechanics.
A few lessons from a qualified batting coach is by far the best investment you can make in your son or daughter's time at the plate. Nothing is more exciting then seeing them take command at the plate and driving the long ball.
Dad said it's OK to hit - a baseball