If Real Madrid wins, the points will be reduced and their chances of winning the Laliga title will increase because they will generate more confidence in the match and the way they just pick form they can do well to close more gap because every team has a high tendency to drop points.
With the results of the el classico's that have been played this season, it looks like Xavi and Barcelona know how to beat Real madrid, they are going to meet two more times this season, there will be an el classico on Sunday in the La Liga, and another on the 5th of April in the copa del rey semi final second leg. I don't know if Barcelona can win the both of them, but it is something that can happen.
On Sunday, if Barcelona win, they are surely going to win the La Liga, but if Real madrid win, they would reduce the advantage that Barcelona has to 6 points, and then try to chase them as much as possible, i believe this game will end in a 1-1 draw, and it will be a very good result for Barca, then on the 5th of April, i predict that Barcelona are going to qualify for the Copa del rey final.