Gimpy,
The .38 is a good choice. Was the LEO caliber of choice for many years. We got a Ruger SP101 .357 for the wife cause she couldn't rack the slide on an auto. She shoots .38 special + P for SD and loves it. I got a Ruger LCP .380 for a BUG and it's become my warm weather primary. I say now I wouldn't go lower than a .380, but for years and years my primary was a .25 auto. It did stop a carjacking/robbery with no shots fired, so I guess it did it's job. ANY weapon can be a deterrent, although Treo is right (for once) about so many .22's being the reason for so many deaths. Almost everyone has one or two .22 handguns and rifles. Usually bigger is better, but CC does require compromises. If I could conceal a Ruger Blackhawk .41 Magnum (my favorite handgun of all time) with an 8" barrel, it would be my only CCW.
The caliber used, as a rule, is a compromise for CCW, but ANYTHING is better than nothing for SD.
"We must reject the idea that every time a law's broken, society is guilty rather than the lawbreaker. It is time to restore the American precept that each individual is accountable for his actions." - Ronald Reagan