David replaced Saul as king. David and Saul were alike in these ways:
Samuel anointed both.
Neither was pursuing the position of king.
Both were unlikely choices (Saul was from the smallest tribe, and David was the youngest son).
They were both good-looking (1 Samuel 9:2; 16:12).
The Spirit rushed upon each when anointed as king (1 Samuel 10:10; 11:6; 16:13).
The main difference was that David was "a man after [God's] own heart" (1 Samuel 13:14; compare 16:7), while Saul was not.