Well, some of these are personal opinions and observations but here you go...
1. A longer, heavier first pull provides a useful "stress buffer" - this, to me, is the big one. HUGE.
2. Decocking and then thumbing the hammer when reholstering provides an additional level of safety. (Important to me as an AIWB guy.)
3. Carrying a TDA gun decocked makes it a point and shoot device, like an easier to use SA gun (or a "safer" SFA gun) but with the above benefits.
4. Once mastered, a DA trigger pull allows you to be more aggressive on the trigger on the press out ... without compromising safety.
5. I shoot TDA guns better, faster. I am more accurate with the first shot and faster with the followups.
If I were to carry something cocked and locked I would be VERY particular about how the safety operated. How ergonomic is it? How much force does it take to disengage and engage? Does it physically lock the slide? A light SA pull is not something I take, uh, lightly