Wildcard certificate is suitable for protecting multiple subdomains on a single domain.

If you need to protect multiple domain names within same organization or secure multiple services (OWA, SMTP, Autodiscovery, ActiveSync, and Outlook Anywhere) in Exchange 2007 or 2010, then the UC/SAN certificate might be the right choice. In addition, you can add, delete and change additional domains except the primary domain over the lifetime of the certificate by SSL reissue.