Assuming these are target loads I would drop the spring to 16 pounds in the Dan Wesson. Stock in a GM size is usually 18 pounds IIRC.
A 20 pounder in a Commander usually will not reliably function at target SWC velocities. Also sometimes those new pistols seem to be a tad tight even though they feel nice and smooth when you work them by hand.
The best gun for self defense? Any loaded one will do.