Sold my 340PD and kept the Kahr PM9. The Kahr shoots better for me, is only two ounces heavier than the Scandium J-frame, carries six or seven rounds rather than five rounds, reloads quicker, and 9mm +P is more potent ammunition than .38 spl +P. While .357 magnum is more powerful than 9mm, the recoil in a 340PD with .357 magnum is so intense that S&W warned about bullets moving forward in the cartridges, rendering the pistols temporarily inoperable.
Some folks can competently shoot .357 magnum in a 12 ounce J-frame, but I could not get off meaningful subsequent shots. The PM9 was better for me, but the J-frames are fine guns and might be better for you.