> germanium diodes generally have a softer turn-on than silicon diodes

This a million times, and it also applies to germanium transistors too. I keep reading that all it needs to emulate the germanium sound in a guitar fuzz made with silicon transistors is adding a small cap between base and collector, which is only part of the story: those are non linear devices, and there's a non trivial difference between Ge and Si V/I curves, which translate into different sound which can't be emulated just by adding a cap. A softer curve creates a much gentler distortion which doesn't ruin the sound when playing chords for example.