If At. Madrid wins against Barcelona becomes the favorite!
Even if they win against barcelona, it is not a guarantee that they will win the championship. They will only close the gap into two points but that means if barcelona lose another game then they will be able to take the lead. I cant imagine that barcelona will want this to happen as they want to secure the title as well this season
For me the match will end with a draw (1-1), the Barcelona will keep the 5 points of advantage and will win the Liga.
At home the Barcelona is practically unbeatable in fact in 19 rmatches (Liga, Copa de Rey and Champions League) has got 17 wins and 2 draws.
But if the At. Madrid winning at Camp Nou becomes the favorite because psychologically it would be stronger.
The worst-case scenario for Barcelona is if ATM take over the lead at Camp Nou because it will make Barcelona job getting harder to manage to compete in all three important championships. In other hands, it will surely be a huge mental boost for ATM.