Good question. ...
Turns out that college baseball players (if using the SEC is an indication) are much less likely to hit HR than MLB players or college softball players ...
SEC baseball vs. softball per 600 at-bats
HR - 8 - 20
SO - 103 - 105
AVG .265 - .259
So you are more than twice as likely to see a HR in a SEC softball game than in an SEC baseball game. Didn't the NCAA put a restrictor plate on baseball bats? That might explain something.
But what I find interesting is that MLB hitters hit HR twice as frequently w/ wood bats as SEC hitters using metal. Of course, MLB hitters are older and stronger physically. But they're also facing the best pitching.
Something like that. They are supposedly set to perform with similar charatersitcis to wood bats with the durability of metal I I remeber right.
The fence distance in baseball/softball may also have something to do with the number of HRs.