Only a couple folks, AFAIK, own both versions so just wait for their responses. I know Navy87Guy owns an M9, Glock and P99 so he'd be a good sou8rce for info. In the meantime, a link to his website is below. Would like an M-A1 one day to match my M9.
http://users.adelphia.net/~navy87guy/index.html
http://users.adelphia.net/~navy87guy/index.html