I'm getting very close to buying my first (most likely only) handgun. I've settled on the compact size versus full size or sub-compact. I'm drawn to the Gen 4 Glock 23 or 32 because of the ability to convert to two other calibers. I really like the idea of having that versatility. In either case I would get a 9mm conversion barrel and mags and primarily shoot that at the range and use the other caliber for SD. I've shot both 9mm and 40 S&W in Glocks so I know how they handle and I shoot roughly the same with both. I've never shot .357 SIG but I like what I've read about it. I know the ammo is quite expensive but if its only for SD, I won't be shooting tons of it. (I understand the need to run a few hundred rounds through a new gun to establish reliability, to spend some range time with your SD ammo and to routinely rotate through existing SD ammo.) Actually my biggest concern with .357 SIG is if I ever have to fire it without ear protection in a SD situation. From what I've read, it's quite a bit louder than other rounds and I'm wondering if I'd suffer permanent hearing damage. I'm also curious about recoil although I've read posts claiming it's no worse, or possibly less than, 40 S&W. I'd appreciate some confirmation of that.