Normally I would say that you should use a query for a form/report as opposed to just setting the table name in there. For forms, the important piece can be that you can sort the query whereas the table is just a potential mixed up set of data (Access doesn't store records in any particular order in the tables and you can get a varied view each time you open it, depending on what has been added/deleted, etc.).
Also, you can use queries to limit the amount of data coming in which can enhance performance. Only pull what you need.