40 is and will continue to be one of the BEST defensive handgun calibers on the market. While the development of ammunition has helped the 9mm make a comeback, it is the price of ammo and the light recoil that have people who don't know about ballistics choosing the 9mm in greater numbers than 40. I have both, shoot both, like both but I would not say 9mm is better than 40. A 155 grain 40 load at 1150fps will smoke most any 9mm defensive load and the 135s perform similar to a 125 grain 357 mag. Even a plain vanilla 180 grain 40 load is very effective as a stopper. The 9mm tends to need more high performance ammo to compete with 40 in terms of penetration.
There is no real advantage to 9 in full size, all steel handgun like a CZ 75. The HUGE advantage of 9mm is you can put it into a small defensive gun that used to be only be available chambered in 380 and it will still be controllable compared with the much more powerful 40. Ask people how they like their K40 Kahrs. Small polymer 40s are worse and will beat you up. The K9s are very well balanced, accurate, controllable and pleasant to shoot (when they will run right). Even a 45 in a full size 1911 is controllable. Put that same cartridge in a 3 inch sub compact and you won't enjoy shooting it very much. Is 40 dead? No more so than the full sized 1911 pistol in 45.
There is no real advantage to 9 in full size, all steel handgun like a CZ 75. The HUGE advantage of 9mm is you can put it into a small defensive gun that used to be only be available chambered in 380 and it will still be controllable compared with the much more powerful 40. Ask people how they like their K40 Kahrs. Small polymer 40s are worse and will beat you up. The K9s are very well balanced, accurate, controllable and pleasant to shoot (when they will run right). Even a 45 in a full size 1911 is controllable. Put that same cartridge in a 3 inch sub compact and you won't enjoy shooting it very much. Is 40 dead? No more so than the full sized 1911 pistol in 45.