Good catch.
It's the 2005 one.
According to the following definition in the SQLServerDQE /DynamicQueryEngine.cd
private static SqlServerCompatibilityLevel _defaultCompatibilityLevel = SqlServerCompatibilityLevel.SqlServer2005;
Also in the generated DataAccessAdapter.cs it's mentioned that the default is 2005
private Nullable<SqlServerCompatibilityLevel> _compatibilityLevel = null;
public Nullable<SqlServerCompatibilityLevel> CompatibilityLevel
{
get { return _compatibilityLevel; }
set { _compatibilityLevel = value; }
}