Crystal Reports :: Single Report For Parameters & All Records?

consider the example where there is a report which displays all products or a single product from a table through a drop down list selection. The dropdown list also has a '- ALL -' selection item So the resulting query might be

Select * from products OR
Select * from products where ID={id}

Now I have a single report , I am using sql CASE for differentiating between all products or a single product. Another approach is to pass a different value with where clause in report parameters like

[Code]....

What I like to know is what is the best approach? Is doing this inside query is best or specifying the where clause in the report parameters is right? I personally feel much safe with the SQL query CASE.