SQL & PL/SQL :: Using Sequence.NEXTVAL From DUAL Versus In INSERT Statement?

I am trying to understand the difference between using sequence.NEXTVAL from DUAL as against using it direclty in an INSERT statment.

--Sequence Creation
CREATE SEQUENCE SEQ_ID START WITH 1 MINVALUE 1 NOCYCLE CACHE 500 NOORDER;
--Table1 Creation
Create table TABLEA (COL1 number, COL2 varchar2(10),
constraint COL1_PL primary key (COL1));
--Table2 Creation
Create table TABLEB(COL3 number);
alter table TABLEB add constraint COL1_FK foreign key(COL3) references TABLEA(COL1);

-- Option1 - Using sequence.NEXTVAL from DUAL

DECLARE
v_seq_num NUMBER;
BEGIN
SELECT SEQ_ID.NEXTVAL INTO v_seq_num FROM DUAL;
INSERT INTO TABLEA (COL1, COL2) VALUES (v_seq_num, 'test');
INSERT INTO TABLEB (COL3) VALUES (v_seq_num);
END;

-- Option2 - Using sequence.NEXTVAL in INSERT USING RETURNING INTO clause

DECLARE
v_seq_num NUMBER;
BEGIN
INSERT INTO TABLEA (COL1, COL2) VALUES (SEQ_ID.NEXTVAL, 'test') RETURNING COL1 INTO v_seq_num;
INSERT INTO TABLEB (COL3) VALUES (v_seq_num);
END;