Which is better UDF or STUFF function ?

Hi,

We have a requirement like to retrieve a concatenated string of values as a column. For this whether i should use UDF with SQL query or STUFF.

Please suggest.

Here is my Example
------------------

--Create function
CREATE FUNCTION dbo.GroupsList(@AgentID NVARCHAR(32))
RETURNS NVARCHAR(MAX)
AS
-- Returns the grouplist
BEGIN
    DECLARE @listStr VARCHAR(MAX);
   
    SELECT @listStr = COALESCE(@listStr+',' ,'') + g.GroupName
 FROM
  AgentIDGroup ag 
  INNER JOIN Groups g
  ON ag.idindex = g.IDOrPhoneNoIndex
 WHERE
  ag.AgentID = @AgentID;
  
     IF(@listStr IS NULL)
        SET @listStr = '';
       
    RETURN @listStr;
END;
GO 
 
--Call UDF to get resultset
SELECT
 a.*
 ,dbo.GroupsList(a.PhoneUserID) as GroupsList
FROM
 Agents a

--CTE with STUFF function and XML PATH clause
WITH CTE AS (
SELECT AgentID,
STUFF((SELECT ', ' + rtrim(convert(nvarchar(32),G.GroupName))
FROM   AgentIDGroup AG1 JOIN Groups G on G.IDOrPhoneNoIndex = AG1.idindex WHERE AG.AgentID = AG1.AgentID AND G.GroupFlag = 0
FOR XML PATH('')),1,1,'')
GroupsList FROM   AgentIDGroup AG GROUP BY AgentID )

SELECT A.*, ISNULL(CTE.GroupsList,'') as GroupsList
FROM Agents A LEFT JOIN CTE on A.PhoneUserID = CTE.AgentID

--In both case the output will be like this
------------------------------------------------------------------------------------------------------------
PhoneUserID | FirstName | LastName | MiddleName | GroupsList
------------------------------------------------------------------------------------------------------------
6001                 Jill              Steeves          J            test group,Delegates

Thanks,
Bijay