The S&W Safety Hammerless break-open revolvers have an excellent DA trigger - the pull is moderately heavy, but has a definite stop point, which can be felt, just before a small final increase in pressure releases the hammer. It permits DA shooting with a final trigger pull very much like a single action revolver - I wish modern revolvers were available with such a DA trigger. The greatest objection to these revolvers in my experience is the very small sights, and a front blade which is short enough that most of the guns shoot very high of POA at usual revolver ranges. The .38 S&W cartridge is no fireball, but is actually a fairly effective SD round, and the Safety Hammerless revolvers are safe to carry, easy to use, accurate and reliable, all of which makes them a decent choice for SD. Other brands of break-open revolvers are less desireable, in my experience, and I'd choose the S&W over any of them.
PRD1 - mhb - MIke