Why DA only(hammer fired)....
This is a simple but important question to many new handgun owners or entry level armed professionals/sworn LE officers all over.
In plain terms, DA only pistols or revolvers offer a safe, practical way to carry or deploy a sidearm in a lethal force incident(sometimes called a "critical incident"). Author, tactics trainer, sworn LEO, and legal use of force expert Massad Ayoob,
www.MassadAyoobgroup.com , has put out may magazine articles & reports about why the DA only type firearms work best for carry/protection.
US law enforcement agencies from the NYPD to the LAPD & federal LE agencies like the US Border Patrol & ICE(Immigration & Customs Enforcement) use or authorize DA only sidearms like the SIG P226/P229R, the HK2000(lem) & the older S&W 5946(9x19mm).
Many law enforcement agencies in Canada issue DA only service pistols too.
DA only pistols or revolvers reduce the chance of false or bogus claims of "cocking" a handgun's hammer or being reckless and firing due to the light trigger pull.
A legal case in Miami Florida in the early 1980s where a uniformed LE officer shot a teen as he played a video game was a big part of the DA only sidearm change in SOP(standard policy). Some lawyers claimed the cop "cocked" his DA/SA Smith & Wesson revolver then fired by "accident". Miami had many riots & civil disorders due to this high profile event.
FWIW; The ATF,
www.ATF.gov considers the Glock model a DA only pistol. Glock & Gaston Glock(the designer & "father" of the Glock pistol) call it a "Safe Action". I, myself, lean more towards the duty or concealed use of hammer fired pistols like the Beretta PX4/C, the SIG Sauer P226/229/239 DAK or the HK P2000/HK45/P30 with the LEM(law enforcement modification).
Some handgun shooters or armed professionals prefer the Glock/Kahr/M&P/XDm etc but I'd say it's better for advanced or trained gunners.
I also prefer the spurless or DAO type handguns with no spurs. It conceals better, speeds ignition & won't snag or get hung up on garments.
DA only handguns may not be right for everyone, but they may be right for you.