IMO, using -3 or heavier wood bats at 12u up to HS is beneficial mostly because it makes you stronger very fast. There is no better way to develop bat speed than to swing 100 + times a day with a heavy wood bat. We have had great success with wood. Good for conditioning too. Do 4-6 rounds of front toss in a half hour and it is a good workout. You can end the session with your gamer.