Q:

sp_dropuser stored procedure vs drop user statement in tsql

As the title suggest, which choice is preferable (in what conditions if any) for removing a user from the database: sp_dropuser stored procedure or DROP USER command ?

A:

sp_dropuser is being deprecated in favour of DROP USER.
To quote MSDN here:

This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. Use DROP USER instead.

Therefore DROP USER is the one to go with.
The same holds for other similar stored procs such as sp_adduser.

