When to use Decode instead of Lookup Transformation

Lookup transformation we use when we have a scenario where we need to lookup from various target and pass the value ,so instead of using all the lookup tables in the mapping what we can do is to include one lookup and fetdch the require value from all the tables and pass to the target.

The same logic can be also done using Decode statement.But in can only be done for small set of unchanging values.While using decode Informatica server doesnot have to lookup up seperate table,the values are brought into the expression itself whereas for lookup Informatica server needs to lookup table from database.