Aside from the practical/operational differences there's one thing I like
to point out to fans of non-Listserv automatons.  AFAIK all of the other
products are programs running on single systems with no "knowlege" of the
rest of the Internet.  Listserv is part of a network of Listservs who
chat with each other, do load distribution, warn each other about spammers
and update each others data.  And plenty of other stuff that I may not
be aware of.  On the non-list-distribution side of it, CataList takes the
WWW Interface and acts as the central hub of all the Servers.

                                                 -Kary