It's difficult to make specific statements about the viability of
LocalTalk over Ethernet or Ethernet over LocalTalk without knowing more
about the customer's environment. Two important factors to consider are
the number of potential users on the network, and the actual type of work
they do over the network (that is, file sharing, mail, database, and so
on). It's not too difficult to come up with a few graphs to show the
difference between LocalTalk and Ethernet transfer rates, but it really
doesn't tell the whole story or justify the expense of moving to Ethernet.
LocalTalk uses CSMA/CA and Ethernet uses CSMA/CD. A certain amount
of overhead is associated with CSMA/CA which is not needed in a CSMA/CD
(Ethernet) environment. The bandwidth of a LocalTalk network can be
dominated by a single node doing a single file transfer. Ethernet has
plenty of bandwidth available, which makes domination by a single node
almost impossible. On the other hand, LocalTalk is basically free and
Ethernet requires a significant investment in hardware.
Ethernet is definitely the best choice for anyone contemplating large
numbers of users accessing a shared resource and/or anyone who may have
significant data transfer requirements. It sounds like you fit this
description. Remember that networks usually grow larger and more complex.
With more demanding network-based applications predicted for the future,
LocalTalk may be a viable topology only for small workgroups that only
transfer an occasional file and/or read mail.