Nmh (new MH) itself was originally based on the package MH-6.8.3, and
was intended to be a (mostly) compatible drop-in replacement for MH.
In contrast, mmh is not intended to be a drop-in replacement for nmh,
-rather mmh breaks compatibility to nmh in order to modernize and
-simplify it.
+but rather aims for the modernization and simplification of nmh,
+accepting reduced compatiblity if it, at the same time, allows to
+achieve greater goals from mmh's point of view.
Mmh is small and simple; nmh is established and matured; MH is ancient.