I have a M&P .45, fit my hands better then the Glock. Grips on a Glock just don't work for me.I would really like a Glock or M&P with a frame mounted safety. The M9 is way too big in the hands, and I have big hands.
I think the M9 with adjustable back straps will take care of most fit issues, some people are just too big, or just too small.
M&P has fixed the trigger issue, so I think it would make a nice pistol.
Does Glock have a US Factory? Berry compliance could take them out of the game.
In the end it won't matter. beretta has the contract, they can buy A3's under that contract and probably will.
Beretta parts will fit either model in stock, and that will drive the procurement decision.