If you're strictly talking turn of the 20th century pistols, it's a bit of a niche comparison and not very relevant to the choices available today.
The real leap in small self defense pistol technology arguably came in the early 1930s with the PP series pistols - and they are considered old by both chronological and technological metrics.
A more practical comparison is the blow back operated, double action, de-cocker equipped PP series pistols in .32 ACP and .380 ACP with more modern delayed recoil locked pistols in .380 ACP like the Kimber Micro.
A PP or PPK/S is a pleasure to shoot in .32 ACP, but in .380 ACP, particularly a stout self defense load, the blow back operated pistol is less pleasant and has some bite to it. Not enough to matter over a short range session, but enough that you don't enjoy putting 100 rounds or more through one. And, it's enough that it requires additional training for the shooter to get good with it.
In contrast, the Kimber Micro's 1911 style delayed recoil locked breech system requires a much light recoil spring and the slide is much easier to operate. It also has much less "perceived" recoil, when in fact it actually has more total recoil given it's lighter weight, but the recoil is spread out over more time and has less "bite" to it.
The Kimber Micro is lighter and smaller than a PPK/S and is every bit as reliable - and with one of the several loads using the 90 gr XTP hollow point, it will come very close to meeting the FBI's penetration and expansion requirements.
In fairness, the PP and PPK/S with their longer barrels (3.5" and 3.9" compared to 2.75") and greater ballistic efficiency will actually meet the FBI requirements with the 90 gr XTP at around 1000-1050 fps.
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With all that said, I have no qualms carrying either one, but at the end of the day when everything is considered, my preference for a an armed citizen self defense shoot is still a steel J-frame revolver like the Model 36 or Model 60. With a well chosen .38 +P self defense load, it will also meet the FBI penetration standards and is also very enjoyable to shoot when equipped with a decent set of rubber grips.
