Your choices in PPK/s models are as follows:
German/French.
Made in France by Manurhin, proofed and finished in Germany and marked "Made in Germany".
Excellent guns.
Manurhin.
After the license with Walther expired, Manurhin imported them under their own name.
Same gun as the German marked, just with Manurhin markings.
Excellent guns and a good deal, but were only available a couple of years.
Interarms made in America.
After the license with Manurhin expired, Walther licensed Interarms to make them in America.
Actually made by Ranger in Alabama.
The first PP series made in stainless steel as well as blued.
Quality was usually very good, some later models had quality issues.
In between Interarms and S&W.
Assembled from parts.
Had no Interarms stamps. Quality varied.
S&W.
Currently made by S&W in a separate production plant.
A slightly modified licensed copy.
The frame tang is longer to prevent hammer bite or slide cutting of the hand. Grips will not interchange with older versions.
Early guns had quality issues, and a recall was done due to a possible problem with the firing pin safety system.
Current guns are getting a very good reputation.
Preference:
If you can find and afford it, the German/French or Manurhin versions are trouble free. and the highest quality.
Price is high.
The Interarms is good, but buy one made before the later few years.
The S&W is getting good and has a lifetime warranty if you do have trouble.
Pointers:
Use ONLY genuine factory magazines in whatever version you get. After market very often cause trouble, which gets blamed on the gun.
Be prepared to experiment with ammo to find a brand/type your specific gun "likes" and is reliable with.
Keep the gun lubed. I always used a good grease since that doesn't dry out or run off.
Polishing the feed ramp may be necessary on later production Interarms and S&W guns, but DO IT RIGHT, and don't try for a mirror bright shine. You just want smooth.
Don't try installing lighter mainsprings, these too often cause reliability problems. The DA trigger is heavy and you just have to get used to it.
Once you do, you won't notice it.
Don't install heavy-duty recoil springs. The gun was engineered to use factory weight springs, and other springs may cause reliability problems in small pistols.
Watch out for limp-wristing the gun, which may cause reliability problems.
It's a .380, but you still need to hold on to it firmly.