The ministry of David and the ministry of Saul are in sharp contrast to one another. God chose David and the people chose Saul. David was a man after God's own heart and Saul was out to make a name for himself.
The ministry of Saul represents that ministry that is established on a title without the inner preperation of the heart. The ministry of David is that ministry which is ordained of God and established through the dealings of God and much inner preperation.