Sql server Merge alternative(left join/if not exists) ---better performance than merge

 -- MERGE 

MERGE #Target t

    USING #Source s

    ON s.ID = t.ID

    WHEN MATCHED

        THEN     UPDATE

            SET Value = s.Value

    WHEN NOT MATCHED

        THEN     INSERT

                ( ID, Value )

            VALUES

                ( s.ID

                , s.Value

                );

-- UPDATE/INSERT

BEGIN TRANSACTION T1; 

UPDATE t

    SET Value = s.Value

    FROM #Target t

    INNER JOIN #Source s

    ON s.ID = t.ID;

INSERT INTO #Target

        SELECT s.ID

              , s.Value

        FROM #Source s

        LEFT JOIN #Target t

        ON s.ID = t.ID

        WHERE t.ID IS NULL;

#################################

insert into [SubProjSchema].[Products]([ProductName],[ProductId],[UnitPrice],[CreatedBy])

SELECT [SPTI].[ProductName]

  ,[SPTI].[ProductId]

  ,[SPTI].[UnitPrice]

  ,[User]

FROM @p1 [SPTI]

left join [SubProjSchema].[Products] [PRD] on [SPTI].[ProductId] = [PRD].[ProductId]

where [PRD].ProductId is null

insert into [SubProjSchema].[Products]([ProductName],[ProductId],[UnitPrice],[CreatedBy])

SELECT [SPTI].[ProductName]

  ,[SPTI].[ProductId]

  ,[SPTI].[UnitPrice]

  ,[User]

FROM @p1 [SPTI]

WHERE NOT EXISTS(SELECT 1 FROM [SubProjSchema].[Products] [PRD] WHERE [SPTI].[ProductId] = [PRD].[ProductId])

#################################

COMMIT TRANSACTION T1;