9mm is not a problem if you use the right ammo, and put two rounds center of mass, then finish off with one to the head. (allways train double tap, then final tap... LOL)
I've owned a Tarus PT92 in 9mm for years, and it's a great gun. Have a stock 15 round mag, a larger 17round mag and just bought a 30round mag for fun plinking. (I've put about 1500 rounds through this gun over the years, possibly more, and never, ever had one jam, or fail to fire.)
I've shot 9mm glocks, the GAP45 glock and the 40 cal version too.
My brother just bought the FN5.7 and it's a kick ass weapon. 20 rounds in the mag, awesome accuracy and that bullet is pretty wicked to body armor. (Heck, you can't buy the teflon coated bullets anymore, but they will go right through most kevlar based personal armor.)
Best part of this gun is the recoil... what recoil? (One of the things I like about my 9mm is you can learn to shoot it quickly and accurately due to the controllable recoil v/s say a 45 or other large bore pistols.)
I'm not saying you can't become accurate with larger guns, it's just not as easy to put 3 rounds into a target when the gun is bucking in your hands with every pull of the trigger.
Few years ago, I was shooting with a friend of mine at the dump.. (I love parts of Idaho, the dump is open year round, and there is NOBODY there after hours, so you can shoot up whatever is there that day. TV's, washers and dryers, old fridges and other cool stuff to shoot. Anyway, we were shooting this old fridge, and had just used a marker to outline some targets on the thing. I could put double taps into these 3" rings very quickly, but he was not because his 1911 was jumping all over the place.. we swapped guns, and suddenly I could not hit shit on the second round, but he became very accurate..
So, the 45 will only do it's job if you can keep it on target... LOL (Or hope to stop the bad guy with one round... good luck on that.)