747b0392__5_1___Postgres_OnLine_Journal__Microsoft_SQL_Server_2008
[Feature] Authentication [MySQL 5.1] Standard Db with table-driven IP like security [PostgreSQL 8.4] Extensive - standard, LDAP, SSPI (can tie in with Active Directory if running on NT server, but still not quite as nice as SQL Server seamless integration), PAM, trust by IP, etc. [Microsoft SQL Server 2008] 
Standard Db security and NT /Active Directory Authentication
Cross Compare of PostgreSQL 8.4, SQL Server 2008, MySQL 5.1 - Postgres OnLine Journal
Microsoft SQL Server 2008