OK, here goes the can of worms, LOL
1) The guys in the Military want to get away from the 9m/m and go back to the 45.
2) Most police dept's have switched to the 40 S&W.
3) If you think about it, the 9 m/m is about the equivelent to the 38 spl. as for as power goes (a little faster but a little lighter, does shoot flatter though).
4) The FBI, moved away from the 9 m/m years ago due to bad performance ( yes there has been improvements in ammo construction since then with a great choice in premium ammo, but the same would go for IMHO the better caliber choices of 40 S&W, 45 ACP, 45 GAP, 45 SUPER, 38 SUPER, 357 SIG, which for the common calibers I would recommend 45 ACP, or the 40 S&W as first choices) and went to 40 S&W after some testing of the 10m/m.
5) The FBI has also started going back to the 45 ACP in recent years.
6) Faster, without using premium ammo can cause over-penatration, which is not such a good thing in a carry gun. This was part of the problem the FBI had at the time with lack of reliable expansion.
Now with all this said, I do own a 9 m/m, but not for carry. I use it for plinking and small game hunting. for carry I use my 45 Colt Combat Commander, Sig 229 40 S&W, or my S&W 686 357 mag as a road gun when traveling. The 9 is effective enough for a carry gun, and it is only "MY OPINION" but, I think that there are better choices out there in pistols of approximate size. The choice is up to you of course. Just my 2 cents though, good luck on your choice and have fun...JOHN