Say you have a model Person. Each Person object can have many Friends (Field_HasMany).
If you want to get a simple array of name/id pairs for a given Person's friends, is it faster/better to get the Friends like so:
$friends = $person->friends;
and then create an array from that object with a foreach loop
OR
do a select, like so:
$friends = Jelly::select('friend')
->join('people')
->on('person.id','=','friends_people.person_id')
->where('person_id','=',$person->id)
->execute()
->as_array('name', 'id');
Basically what Jelly does is build the correct query when you request a $person's friends (which is similar to your custom query)
To get friends in an array, you can do exactly the same thing as you're doing with your custom query:
$friends = $person->friends->as_array('id', 'name');