There have been many studies done. ESPN and HBO both had features about it. All the studies I have seen show that the exit speed is far greater off the aluminum bat. That is why they changed the legal limits of the metal bat instead of going to the most sensible thing, go to the wood. The only people arguing on behalf of the metal bat were oddly enough the metal bat manufacturers. They are the only loser if everyone goes to wood. Haven't they raked everyone enough already with 500% profit on a metal bat. They have enough money to do any scientific study they want to absolutely prove their safety. Yet most the studies are conducted by others. They don't need or want the studies because they buy out college baseball with free product to the big teams. Then all the others pay big dollars to make up for it.