PPK >< J-frame
More or less everything I could add has already been said, but I'm willing to share my own experience with both my Walther PPK .380 and S&W mod 640 (steel, not airweight).
It would be a painful choice but if forced to, I would prefer to keep my 640 and let the PPK go.
DA trigger pull on the Walther actually feels not bad at all, even better than that on my CZ-75B 9mm.
Also, I don't have large hands, so the PPK never "bit" or cut me.
It's just about as accurate as my 640, & has higher round capacity.
It does however recoil sharply and unpleasantly.
I blame that on the grip shape : with the factory (flat, plastic) grip panels I can hardly shoot it at all. So far the only substitute I found are wood NILL grips , which are beautiful but very expensive & do not really fit my hand perfectly.
(Someone mentioned Pachmayrs that wrap around the backstrap, but my PPK doesn't
have any backstrap at all )
My biggest problem with my PPK is its less-than-100%-reliability. Failures to feed are too common fro a SD pistol, about twice tot three times per 50 rounds.
The 640 on the other hand has an unblemished reliability history, and with Pachmayrs compac grips or Uncle Mike's, I can control it better than the Walther,even when shooting rather -for me- stiff .38 spl loads (158 gr. swc & 5.3 gr W-231).
Therefore, although I have no experience with Airweight J- frames, strictly for SD, I would opt for the S&W.
On the other hand, I think my PPK is way cool, & I' m keeping it anyway.