The best 9mm rounds approach the stopping power of the big three (.357 Magnum, .40 S&W and .45 ACP), but a wider range of the big three rounds are effective stoppers.
If capacity is more important to you than having a wide range of ammo to choose from, then go with the 9. If having a wide range of ammo to choose from is more important that capacity, then go with one of the big three.
If capacity is more important to you than having a wide range of ammo to choose from, then go with the 9. If having a wide range of ammo to choose from is more important that capacity, then go with one of the big three.