Not an expert. I have a DA/SA Sig 229, and 1911s. Have shot, but don't own Glocks.
SA only:
pro: great trigger pull
maybe a bad guy who grabs your gun won't know how to use safety
con: you must train enough to activate/deactivate safety instinctively.
there are real world incidents of people dying because they forgot to disengage
safety in a close range fight, or shooting themselves on the reholster because
they forgot to reengage safety (and keep finger off trigger)
DA/SA:
pro: can't forget to disengage safety
heavy DA trigger might prevent some negligent discharges
con: must train for DA to SA transition
in a gun grab, bad guy won't be stopped by safety
must train to decock before reholster or same as SA only...
Glock style:
pro: can't forget to disengage safety
same trigger pull for all shots
con: if not an NYPD trigger, light enough that you better keep your finger off until you
want to shoot; no heavy trigger pull to save you
What's the right answer? I don't think there is one. They all have advantages and disadvantages. Whatever you pick, train until you can't do it wrong. Train, train, train, and train some more. Note that much of this training (SA to DA transition being the exception) can be done via dryfire.