A DA/SA pistol requires mastery of the first double action shot, and the subsequent DA to SA transition, which I think requires a greater period of training than for a striker-action pistol.
Yep, that's my experience too. I've spent over 50 years now as short gun user...on duty, in combat, and for recreational purposes. Tried and trained on all the basic types starting with the venerable Smith and Colt DA revolvers, through the 1911 (still my favorite grip style and shape), to the more modern Beretta 92, Glock 17, 19 & 23's, and 5 Sig DA/SA's.
Of them all, the Sigs were the hardest to transition to...initially causing two different shot placement groupings. The DA shot hitting low and the following SA shot hitting 4" higher at combat distances of 7 yds or more. While I and my experienced shooting buddies can keep the two groups together in deliberate fire; they diverge when any speed from the holster is involved. And yes, it can be corrected by training...but we've found that you really need to settle on that type of trigger alone and train exclusively with it to maintain good grouping proficiency.
I like and carry Sig's for defense (hell, I've got a M11A1 on my right hip as I type this); love their superb quality, accuracy, and great customer service...but their DA/SA triggers are a chore to master and keep proficiency with.
As to the Glocks...I don't like 'em (clunky, plastic, funny trigger feel and no 'soul')...but used one twice at Front Sight's 600 round, 4-Day Defensive Handgun Course to see what all the hoopla was about...as did my wife and a cpl of friends. We found the trigger manageable after a cpl hours of training. They were accurate (5 rounds in a postage stamp sized paster from 7 yds in a Weaver stance), and ABSOLUTELY reliable. The six guns we rented went 2400 rounds without a single malfunction during training.
The three we've owned since then have the same record. They're that good. So why do I dislike them...the grips feel like a chunk of 2x4 to me (even with the modular types), and the spongy trigger annoys me, but I shoot them well...so does my wife. I shot 'Distinguished' my first time through the FS course and won the 'Steel Challenge' shoot off too...and that's with zero time with a Glock prior to training there. For a one gun family, for CC if you can handle the grip issues and the size of the G19 of your choice, they make sense to me. BTW, the trigger/lack of a safety issues are a non-starter for me. Negligent discharges are just that...negligent. Keep you finger off the trigger until aligned with your target...train that way with ALL handguns, ALL the time...and re-holster very slowly, reluctantly may be a better term...you 'feel' the gun down into the holster, stopping for any abnormal 'feel', be it twig, shirt tail, button, what ever.
HTH"s Rod