I prefer a 9mm over a 40, as far is if one is better than the other, I guess it's up to the user. I have both, but as already mentioned 9mm ammo is cheaper, which allows me to practice more. Almost no recoil allows me to stay on target better, and higher magazine capacity, are all things I like about the 9mm. With the modern loads out there now I don't feel undergunned at all. I carry Cor Bon 115 grain plus P's in mine.