What is faster: SUM over NULL or over 0?

Question

I have a query like this:

select sum(case when col1=@arg1 then value else null end) from t

Is there, performance-wise, a difference to use 0 instead of NULL ? Like this:

select sum(case when col1=@arg1 then value else 0 end) from t

Answer 1

DECLARE @type CHAR(2) = 'U'

-- [Expr1042] = Scalar Operator(CASE WHEN [Expr1048]=(0) THEN NULL ELSE [Expr1049] END)

SELECT SUM(CASE WHEN [type] = @type THEN 1 END)
FROM sys.objects

-- [Expr1042] = Scalar Operator(CASE WHEN [Expr1048]=(0) THEN NULL ELSE [Expr1049] END)

SELECT SUM(CASE WHEN [type] = @type THEN 1 ELSE NULL END)
FROM sys.objects

-- [Expr1042] = Scalar Operator(CASE WHEN [Expr1048]=(0) THEN NULL ELSE [Expr1049] END)

SELECT SUM(CASE WHEN [type] = @type THEN 1 ELSE 0 END)
FROM sys.objects

results:

Table 'sysschobjs'. Scan count 1, logical reads 1556, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 7 ms.

Table 'sysschobjs'. Scan count 1, logical reads 1556, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 6 ms.

Table 'sysschobjs'. Scan count 1, logical reads 1556, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 7 ms.

so... answer - similar (if we talk only about performance)