LDAP or ALIASES: Which is more efficient

[subscribed-lists at sterndata.com]

I've been asked to look into building an email forwarding system to support
"branded" email addresses. It's forwarding only. There will be no real
mailboxes, nor will users have id/passwords on the system.

So, I'm planning a set level of spam filtering using SpamAssassin and using
ClamAV and milter-greylist to keep out most of the nastiness.

I am lucky in that we already have the target email addresses in LDAP. I also
have the data in a nearby SQL server. I've been reading sendmail docs and some
O'Reilly books and I'm wondering if LDAP is really the right way to go.  Is it
more or less efficient that generating a new aliases file every X minutes?

Which way would you go?