Improved Manageability – Manageability and governance is important for SharePoint as well as the SQL Server database engine. Now administrators can also benefit from the new management features introduced in SQL Server 2008 – from Policy-based administration to back-up compression.
Backup compression (25-35% at least)
Reporting Services in SharePoint Mode
Policy Based Administration
Easier to deploy
High Availability – Availability in SQL Server 2008 has been improved through enhancements in data mirroring.
Enhanced Data Security – The SQL Server 2008 database engine introduced new encryption functions that enhance security. SharePoint administrators can take advantage of these new encryption features by simply turning on transparent data encryption (TDE). No additional changes need to be made on the SharePoint side.