What is the difference between deep_copy and gen keeping in Specman?

can someone tell me what is the difference between coping one transaction(item) to the another like in examples bellow (add_method_port_1 and add_method_port_2):

add_method_port_1 (added_item: item_s) is {
    var new_item: new_item_s;
    gen new_item keeping { 
        it.my_trans_s == added_item.as_a(t_trans_s); 
    };  
};

add_method_port_2 (added_item: item_s) is {
    var new_item : new_item_s = deep_copy(added_item.as_a(t_trans_s));
};

Where new_item_s looks like:

struct new_item_s like item_s {
    %my_trans_s: t_trans_s;
};

Thanks, Andrija

Actually, the results of the two methods are different even if the assumption mentioned in Rodion's answer does hold.

With the first method, new_item points to the same my_trans_s object as the original added_item, because the constraint it.my_trans_s == added_item.as_a(t_trans_s) means pointer equality.

With the second method, new_item points to a copy of the original my_trans_s, because deep_copy copies everything recursively.