The first son didn't want to obey his father because it was not convenient for him. At least he was honest and told his father NO. Upon realizing his disobedience and sin he repented, and then went and performed his obedient duty.
Son #2 schmoozed his dad and said Sure, I'll go (so as to give the appearance of obedience to his father). But, all day long he decided that pleasing his own flesh and doing his own thing was more important to him than obeying what his father told him to do.
Jesus asks "which of the two did the will of his father?
Point being, if the Word of God says to do something or to refrain from doing something ... OBEY. You may not like it at first but you will be as the first son. Not to obey puts you into the camp of son #2.
Becky