The standard dark gray unpainted plastic grille inserts give it a "new" look while the blacked out grille inserts give it a personal touch.
I've tried the blacked out grille insert approach before and needless to say, went back to stock look. The dark gray is just as good if you want to paint a faded grille insert, instead of black.
My 190E has a very nice dark gray insert and it's new plastic so it's not faded. I agree the quality might be somewhat questionable but only if you really look closely. The edges can be trimmed carefully too.
New insert from the dealer, for the W123 anyway, was $45. The aftermarket is around $20.
Stock W123, unpainted, new:
Same W123, painted dark gray (w/ black headlight surrounds):
Stock W201, unpainted, new:
Stock W124, unpainted, new (notice the old hood pull was not replaced):
