Querying from table using Query Builder

Ok here's the thing both are working just want to know which is more ideal on Query Buillder Doing a subquery or Joining the table?

       DB::raw('(SELECT Name FROM client_types WHERE client_types.id = taxonomy.Type ) AS Type'),                                   
         DB::raw('(CASE WHEN  taxonomy.isVerified = "0" THEN "UNVERIFIED"
                                    WHEN  taxonomy.isVerified = "1" THEN "VERIFIED"
                                    ELSE "UNVERIFIED" 
                                    END) AS Verification'))                                    
                    ->leftJoin('taxonomies as taxonomy', 'taxonomy_pivot.TaxonomyId','=','taxonomy.TaxonomyId');```

also what are the pointers to consider when to Join a table or create a subquery