[exim] LDAP domainlist/hostlist lookups

I am working on optimizing my exim configuration, and have a couple
quick questions regarding LDAP lookups for domainlists or hostlists.

First, which lookup style/type would be preferred?

domainlist mail_domains = \
ldapm;ldap:///ou=Mail,LDAPBASE?associatedDomain?sub?\
(&(objectClass=mail_domain)(associatedDomain=${quote_ldap:$domain})(accountStatus=open))

    -- OR --

domainlist mail_domains = \
${lookup ldapm{ldap:///ou=vMail,LDAPBASE?associatedDomain?sub?\
(&(objectClass=mail_domain)(associatedDomain=${quote_ldap:$domain})(accountStatus=open))}\
{: $domain} {} }


And second, is it better to do a query for a single domain (the one
being handled at the time), or return a list of all domains?

Thanks,

-Mike