Microsoft SQL Server 2008 R2 increases the free SQL Server Express database size from 4GB to 10GB. This means that theoretically the free version of SQL can do larger things without having a full SQL server. Of course there are other factors in that including the robustness of the SQL management tools.
Microsoft SQL Server 2008 R2 has improved protection against SQL attacks over previous versions. It also now supports wildcard SSL certificates which will cut down on your costs as more and more applications are requiring their own SSL certificate.