Yes, it's germanium vs. silicon. In transistors, which are used in amplification circuits, germaniums can (in the right design) sound different from silicon. The broad, sweeping generalization would be that germ sounds smoother and furrier and fatter, while silicon sound sharper and grittier and more "clear" if that makes any sense. Again generalizing, but germ is more "vintage" while silicon is more "modern".
Now all of that is super subjective, and it is also completely dependent on the specific circuit design. There are amp/pedal designs where you could not tell the transistors apart. There are also amp/pedal designs that do not take fullest advantage of the best qualities of each type of transistor, resulting in too much noise or too much harshness or other unwanted qualities. Because of that, you may hear people say "I don't like XYZ because it's too sterile" or something like that- and they're right about what they're hearing in the one case at hand, but it really doesn't apply to all other cases of XYZ components.