I haven't
been in contact with the Kahr. Have examined the KelTec. Personally, I'd take the Walther in .380. But then, I have a weakness for Walthers. I like the PPK/S for three reasons over other guns for this purpose:
1. It feels good in my hand. When I hold one, it fits me, not the other way around.
2. Stainless is great for carry. Low maintenance, and it is a bit more visible than the same weapon in blue steel (although aesthetically, I admit the blue is prettier). Sturdy and well constructed.
3. For it's size, it is fairly flat, and thus I can carry it in my preferred manner (Mexican), but it will also fit in my hip pocket, coat pocket, etc. Maybe someday I'll get an IWB.
In short, I (would) carry the Walther over many others simply because I like it, it's reliable, and I shoot it well enough to have confidence in me/it.
Now, being a certifiable gun-hog, I might pick up something else, given that I might like the Kahr. Did I mention I like the hammer exposed? I don't recall if the Kahr has this. That's one reason I stick to 1911's and Sigs in larger pistols, and don't own a Glock.
The Keltec was a cute little item, but appeared a bit on the cheap side. Dont get me wrong. Heck, I have a Beretta M21. An ok little piece, but honestly a bit on the tinny side. (It's the only semi-auto I've found that my bride can get the slide back on properly. She has some physical problems with this). Her strategy is to empty it while going for the 870.
Looking back over this, it occurred to me that, given where I live, I don't carry anymore, I might not carry any of these if I ever move again to a state that allows it. I have a Sig P245 now, and why in the heck would I be under-gunned? I DO need a holster.