Use Data Loader When:
-
loading 50,000 to 5,000,000 records
-
Work with a Salesforce partner if > 5 million
-
need to load into an object that is not supported by the import wizards
-
want to schedule regular data loads
-
want to export for backups
Use the import wizards
-
< 50,000 records
-
object is supported
-
want to prevent duplicates