The M111 and M104 are very different in nature... seems to me the better comparison is the M112 vs. the M104. Anyway, between the 111 and 104, the 104 is MUCH smoother. I disagree with the description of the 111 being tractor-rough, though. After warm-up, it seems pretty smooth to me.
1988 300 SL (5 Speed)
1994 E320 Wagon