.357 mag, because I carry one or more SP101 snubbies virtually all the time. I often carry more than just the snubby, either one of my personally owned SIG P229 .40 duty (police) pistols, or a larger .357 sixgun. Much as I like my 1911 and single-action sixguns in .45 ACP and .45 Colt, at this stage of my life, they are rarely carried.