Either way you are going to be happy with your choice. The 9mm is a lighter bullet, but a higher pressure caliber, so it jumps a little more than the .45. .45 is time tested, but some people are intimidated by it for some reason. I have 9's, .45's, and .40's, and I like them all, but if I had to take one to a fight it would be my Glock 21 loaded with 230 grain hollowpoints. Good luck man!