Recently scored a 2nd 104, I did a little analysis/comparison (frequency & THD plots) that some might find interesting.
Interesting vids! Side by side the two units produce quite different results. Listening without knowing which unit was on which side really makes you pick what you like. I wasn’t expecting them to be so different. Prefer the 104z personally - raw, gritty, mangling and musical.
Don’t get me wrong, the M sounds like a great delay with its own smooth and delicate / detailed / tuned sound… but the Z is so distinct and stands out in the mix.
Yes, I guess I’m glad I haven’t sold my 104Z to get the 104M. The added features of the M are really, really cool.
Good vids indeed, thanks for taking the time and sharing. 
pretty insane stuff , nice analog rig u made there , the koma pedal looks interesting as well
I obviously like them both. With these videos I was just showing off the delay sections only. The added bonus/gem with 104M is the modulation. I really love adding a slow LFO to the delay tail ( = chorus delay). One of my favorite bass sounds. The 104Z can’t do this on it’s own. But the 104Z’s feedback/self oscillating nature is it’s strength.
You could replicate that on the 104M with the insert i/o plus a stompbox that adds gain to the feedback loop. Everything else aside both sound great, but both BBD chips/Design respond very differently. If I have to pick one it would be the 104M.