Let's broaden it out to the Beretta 92.
I lived through the transition from the M16A1 to the M16A2 and felt we lost more than we gained. I also lived through the transition from the 1911 to the M9 and felt the same.
It wasn't that moving to 9mm made sense, as it did. It's just the form factor of the M9 just didn't work for a much larger percentage of troops than was the case for the 1911. The M9s wide grip and long trigger reach made it difficult for many troops to shoot accurately. That was ironic given one of the selling points was the lower recoiling M9 would be more accurate for troops to shoot.
It's also a large frame pistol shooting a medium frame cartridge and consequently far larger than it needs to be.
I agree the M9 is very reliable when clean (and not worn out). The open top slide design has always been a plus in that regard. But open top slides also allow for a lot more potential for dust sand and dirt to enter the pistol, even in a flap holster. Add in rough phosphate finish magazines and fine desert sand and that reliability went south in a hurry. Add in an excessive and excessively repeated manual of arms and they also started breaking fire control parts prematurely.
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That said, I like the Beretta 92.
The single stack Italian made Compact M is great for concealed carry. Comfortable to carry and easy to conceal, but large enough to shoot extremely well at speed.
The double stack Compact M has the same attributes but more magazine capacity. But that fatter mag causes the same problems that it does in the full size Model 92.
That fat grip is uniquely Beretta as the CZ 75's double stack magazine grip isn't nearly as wide, not much wider than the single stack Compact M.
I still like to carry it, but I had to find ultrathin grips and install a short reach trigger kit, to get the control with it that I want. And while I was at it. I also installed a short reset trigger bar to address the excessively long trigger reach as well as and extended mag release and a low profile de cock lever to address it's other faults.
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In my experience, I US military could have done a better job selecting a pistol during the M9 trials - both of them. They also could have and should have set better ergonomic requirements and then adopted a suitably modified Beretta 92, rather than just adopting the M9 in its basic M92 form.
