I am far from an expert but I do have a fair amount of time on several platforms. For me I always go back to the Glock because I shoot it so well--that means any of their models and anyone's pistol. I prefer a 1911 though as I love the feel of the pistol and I am proficient with it but it is not a beginners pistol or round. Like mentioned above, the 9mm will do the job for several reasons but the major one is follow up shots and placement. it doesn't matter if you have a .45 ACP if you can't hit the target. Remember, keep shooting until the threat is over---9mm allows a lot of rounds on target.