I have carried two J frames, a 640 in .38 and a 3" barrel model 60 in .357. I also carried a PPK for a short stint. Currently I carry neither.
The J frames are great guns, ultra reliable and easily concealed. But, and I mean a big but, they are not the easiest guns to shoot. I am a pretty good shot with just about any pistol, but the J frame is a tough gun to master. Combine an extremely short sight radius, heavy DA trigger, small grip, and minimal sights, it makes for a tough shooter. Now that's not to say I did not shoot the J frame well, it just took a whole lot more concentration to pull of some good groups. Then I picked up a Ruger SR9C and lost all confidence in the J frame. The ease at which I was able to shoot it under stress and in rapid fire completely trumped the J frame. Throw in the fact it conceals just as easily IWB, holds more than double the amount of rounds, and ability to reload quicker, and it was a no brainer to dump the J frame.
As far as the PPK, they are extremely accurate for their size. I shoot the PPK as well as some full sized pistols. It makes a great carry gun IF you get one that works reliably. They are indeed a crap shoot, you might get one that feeds all kinds of ammo and doesn't hiccup, or you might get a jamomatic. Mine would occasionally fail to feed and I lost confidence in it as a carry gun.