Most Efficient (Fast) T-SQL DELETE For Many Rows?

Question

Our server application receives information about rows to add to the database at a rate of 1000-2000 rows per second, all day long. There are two mutually-exclusive columns

Answer 1

Something like this could streamline the process (you would simply INSERT the rows, no matter if they already exist - no need for an up-front DELETE statement):

CREATE TRIGGER dbo.TR_MyTable_Merge 
   ON  dbo.MyTable 
   INSTEAD OF INSERT
AS 
BEGIN
  SET NOCOUNT ON;

  BEGIN TRANSACTION

  DELETE MyTable 
  FROM   MyTable t INNER JOIN inserted i ON t.tag = i.tag 

  DELETE MyTable 
  FROM   MyTable t INNER JOIN inserted i ON t.longTag = i.longTag

  INSERT MyTable 
  SELECT * FROM inserted

  COMMIT TRANSACTION

  SET NOCOUNT OFF;
END

EDIT: Previously Combined DELETE statement broken up into two separate statements, to enable optimal index use.

Not using DELETE at all, but rather UPDATEing the affected/duplicate rows in place will be easier on the indexes.