From my two years working sales in a gun shop, all I can really say is that whatever is most comfortable for
you will be best. You already have experience shooting a DA/SA trigger with the M9. I carried a Sig P226 and really had no problems adjusting to the DA pull out of the holster and the SA pull thereafter.
One thing I have noticed in running training scenarios with someone not used to a DAO (or LEM or DAK) trigger is that they tend to anticipate the shot much more and become frustrated very easily because they pull the gun down before the shot is fired. Now, I know that that is bad form on their part, but it is something else to have to get used to. However, they have the same advantage as guys who shoot striker activated triggers (Glock, Springfield XD, etc) in that the trigger pull is always the same. Whichever way you go, try to keep your trigger systems as similar as possible (KISS).
The question of which would be better for daily carry or a gunfight goes back to you being comfortable. If you're comfortable with and like shooting it, you will shoot it more often. If you shoot it more often, you will become more proficient with it. If you are proficient with it, it will be the best thing for you, regardless of wether it is a DA/SA, SAO (1911), DAO, DAK, LEM, or striker-activated. Hope this helps.
SFK