My wife carries a PPK/S, and I have fired the HK on one occasion.
The recall mentioned on the PPK/S was from a while back. A new gun won't have that problem. We did have trouble with the gun at first, so I sent it back to S&W, and they replaced the slide. It's fired well (through a couple hundred rounds) since then.
The friend with the HK loves it. The grip was exactly the wrong length for me too short to include my pinky, but too long for my pinky to curl comfortably underneath.
The PPK/S works well as a pocket carry gun, which also means it's less fun to shoot at the range. It's narrower than the HK, but has pretty small sights.
The first-round trigger pull on the PPK/S is substantial, but amazingly short.
They're both accurate. I personally don't like the PPK/S sights; I'm not a fan of the dot-over-dot sight pattern. But that's me.
If your primary purpose is fun, the HK is more fun to shoot. If being able to deep-conceal it is more important, I'd say the PPK/S.
"An armed society is a polite society." Robert A. Heinlein
"After a shooting spree, they always want to take the guns away from the people who didn't do it. I sure as hell wouldn't want to live in a society where the only people allowed guns are the police and the military."
William S. Burroughs