357 sig. Get longer range than 45 with some great knockdown to boot.
9mm is garbage unless you want to kill paper.
X2, ur better throwing a 9 at some1, but it boils down to what ur primary purpose will it b used for. I carry a 45, easy to find ammo, tons of knockdown, slow moving, less of a chance of over penetration for hm defense, slower moving n can be completely silenced compaired to the other cal listed unless u buy sub-sonic ammo, but then u take away from their already punny knockdown.