After the last race of the season what determines who wins the Nextel cup the points leader or the winner of the race?

the points leader. The closest the winner of the last race of the season came close to winning the Cup was in 1992, when Atlanta race winner Bill Elliott lost the Cup by a mere 10 points to Alan Kulwicki who finished second in the race (and had led 1 more lap than Elliott to get the 5 extra bonus points for leading the most laps)