To load large amounts of data, it is generally better to use the Load operator, but for smaller load jobs, the SQL Inserter might perform better than most load jobs because it does not need to set up multiple sessions to run.
Also, the SQL Inserter operator does not require an active load job. It simply uses standard SQL protocol on a single session. If it is difficult to acquire database resources for running concurrent tasks, the SQL Inserter operator has advantages over the Load operator.