from LLBL's reference manual
DataAccessAdapterBase.DeleteEntitiesDirectly Method
Deletes all entities of the name passed in as entityName (e.g. "CustomerEntity") from the persistent storage if they match the filter supplied in filterBucket.
IDataAccessAdapter.DeleteEntityCollection Method
Deletes all dirty objects inside the collection passed from the persistent storage. It will do this inside a transaction if a transaction is not yet available. Entities which are physically deleted from the persistent storage are marked with the state 'Deleted' but are not removed from the collection. If the passed in entity has a concurrency predicate factory object, the returned predicate expression is used to restrict the delete process.
does DeleteEntityCollection perform its work directly at the DB or it just loops through the entities in the collection deleting each one ?