I guess I'm going to be in the minority here, but I would go with a 1911 .45 with no reservations. I can't think of any advantage the M9 would offer. There are only a couple of gunsmiths available to civilians capable of producing match quality M9's and they are very expensive. There are many 1911 'smiths who can turn out a match ready pistol. At least for me, the 1911 is easier to shoot.
Phil
