I think I can speak for everyone here when I say we are all glad your brother is one of the "good statistics" that comes out of Iraq.
As far as changing your mind, it is your money and your choice so really about all anyone can do is make suggestions and hopefully back up their opinion with some sort of rational logic. The bottom line is that if you are going to carry, get the largest caliber you can handle and carry comfortably. Obviously you should also talk to your brother (which I am sure you have already) and see what he thinks. While I am sure there are other decorated vets that may be equally as qualified, I would think that your brother's opinion, if anyone's, should matter most of all.