I would say both pistols are pretty iconic of Nazi Germany, but that's getting into the territory of historical subjectivity. Some part of it was the longevity of the P08, having served for forty years by the end of World War II. However, the P08 was replaced (at least partially) by the P38 because the latter was cheaper and easier to manufacture and mechanically simpler.

The P38 had a more lasting influence on firearms design, and was also reissued and newly manufactured as the P1 pistol for the West German military and police. It's still being used today- the German government supplied Peshmerga with 8000 of them. The P38's locking mechanism design strongly influenced Beretta, using the design in the M1951 pistol and the subsequent Beretta 92.