I bought the SIG P-232 stainless based on availability, reputation, reliability, and the lifetime warranty. I've not been disappointed.
As you know, the Walther PPK/S is now manufactured in Maine by Smith & Wesson. The gun has reportedly had numerous quality issues, is notoriously finicky about the ammunition it will accept, and only comes with a one year warranty. My understanding is that S & W is not even shipping any new Walthers until sometime mid to late summer. Still, it is a Walther and I have one on order whenever they resume shipping. Unless, the reliability improves dramatically though, it will never be my primary carry weapon. That responsibility will fall to the SIG which, so far, has performed flawlessly.