I have never owned either, but a former roommate had the PPK and my piano teacher has the P230. So I have fondled 'n fired both weapons to an appreciable degree.
On that basis, my next concealed carry weapon will be a Sig (P230 or P232--I'm not sure I care which). I have no reason to denegrate the PPK, but I will explain my preference for the Sig.
It boils down to this: the design of the PPK slide is "quite pointy in parts."
To work the slide, some people point a handgun upward with their strong hand and grip the rear end of the slide between the thumb and curled forefinger of the weak hand, then pull the slide in a downward motion. Call me an untrained rebel, but I'm not the biggest guy in the world, and I have another technique that is faster and more reliable for me. I hold the firearm in my right (strong) hand, then place the palm of my left hand over the rear of the slide, usually right on top of the sights. (Were I to extend my left thumb all the way, it would point at my right elbow and also indicate the direction the slide is about to travel). This way, I can grip the slide quite securely between all four fingers and the heel of my hand--being careful, on smaller guns, not to cover the ejection port. The slide can then be worked more quickly and forcefully than in the other method by virtue of the enhanced grip, and comes under the pressure of bigger, more commonly used muscles. (Eeesh...spacial relations put tough demands on langauge!) Anyway, if you can imagine this motion, you may understand why the Sig is a little nicer than the PPK for me. It seems that the sight profile on the Sig, as well as the absence of the safety lever make for a less toothy slide, more painlessly compatible with my slide operation method.
I don't plan on changing my slide-working technique, so the next question is this: Would consciousness of a toothy slide cause hesitation in a defensive situation? I don't know, and I don't plan on finding out. Still, I will choose the weapon that minimizes this risk: the Sig.
Good topic!
...Oh...+1 on the Hogue grips!