Either one can be made to work. While the SD40 isn't a small gun, many people can and do conceal guns the same size or larger so long as they're willing to make the wardrobe modifications necessary to "dress around the gun". Similarly, while .38 Special is no power-house, a good loading such as Speer 135gr Short Barrel Gold Dot, Cor-Bon 110gr DPX, or Remington 158gr LSWCHP "FBI Load" make it into a more than capable defensive cartridge that is, IMHO, superior to most of the cartridge commonly found in pocket autos like .22 Long Rifle, .25 Auto, .32 Auto, and .380 Auto.