With ArcGIS 10.2.x, Microsoft SQL Server 2008 R2 Express with Advanced Services was included/distributed for use with Personal and Workgroup SDE. I noticed with ArcGIS 10.3 that Microsoft SQL Server 2012 Express, without Advanced Services, is being included/distributed for use with Desktop Database (fka Personal SDE) and Workgroup Database.
I believe it was ArcGIS 9.3 where Esri switched over to SQL Server Express with Advanced Services. The ArcGIS 10.2.x Help shines some light on why.
The edition of Microsoft SQL Server Express being used for your database server can be determined from the database server Properties dialog box.
XML columns are only supported with SQL Server Express Edition with Advanced Services that have Full-Text Search installed. The Full-Text Search component is required to support the native XML columns used by the geodatabase system tables; when installing SQL Server Express Edition with Advanced Services, you must install Full-Text Search. Other editions of SQL Server Express do not include support for full-text searching.
Obviously, something has changed with ArcGIS 10.3 or SQL Server Express 2012 that is allowing Esri to drop the need for Advanced Services, but what exactly and where is it documented?
I welcome the change for many reasons, one of which being Advanced Services mushroomed the download or package size from ~250MB to the ~1.5GB. Eliminating SQL Server services simplifies installation and administration and could reduce the security-related footprint of running SQL Server Express, which is good in an organization that deploys as many Desktop and Workgroup Databases as the one I work for currently.
This change also piques my interest because it makes me wonder whether SQL Server Express LocalDB support is around the corner.