ssms and sql-management-studio tags both refer to the same application: SQL Server Management Studio. As a result there's no need to keep both tags around.
While 21 questions in each here doesn't give either tag priority, checking other SE sites shows:
Stack overflow has 940 for favor of ssms and ~200 for specific versions; and 219 for sql-management-studio.
Serverfault has 114 for msql-ssms, 18 for ssms, and 20 for ssms-2008; however only ssms has a tag wiki entry. sql-management-studio doesn't exist at all as a tag there.
DBA.SE has 118 questions for ssms and none for any other variants.