Delegation, parenting, and slaves/stubs

[Norman Joseph]

We run a split DNS setup, with separate external DNS authority for our
public face, and internal DNS authority behind a firewall, with
forwarders for external resolution.  Internally, the authoritative DNS
servers for forward & reverse zones are Linux, but subdelegations from
these zones are made to internal Windows boxes.

When we delegate a subdomain (forward or reverse), is it necessary for
the parent zone servers to also run slave zones for the delegation?  If
not necessary, is there any benefit in doing so?  And does it matter
whether you use a "slave" zone or a "stub" zone for this purpose?

Thanks,

-norm