I think both are ok because depends on the case, in search its easier since you call all the implementations using the name of the driver, which is one for all the implementations (per driver of course), while the other cases there's no easy way, unless you base the SC invokes on a naming convention, that some times depends on having the developer to write *well* the impl name, then its just easy to capture the impl_id or in the case of acs-authentication, you choose SC impl by a web form, then makes sense to store it on the DB.
