Too early to decide who wins the league. There are 38 games each of these team plays. The standings at the moment don't actually matter much.
If Barcelona keeps on maintaining wins the overall league than Real Madrid won't be able to catch them but that is highly unlikely. We have seen in past the position changes on later half of the league. Girona was considered a probable winner for the first 19 games but they slipped much lower than Real Madrid or Barcelona in later stage.
Surely it would be Real Madrid and Barcelona that comes first and second. But I think the probability of Real Madrid winning the league is much higher than of Barcelona.
You might not be getting a accurate prediction on who is going to be winning but their are signs and among those three clubs you will be able to choose the one that have a very high chances of winning, their are still enough games for everyone to play their is still room for overtaking so that is why everyone feels that their is still chances for you to be doubt on any club.
And looks like Barcelona is on the way to targeting the league and they have been more consistent than real Madrid and that is because their new coach wants to make a difference. Now people are not really talking about the challenges that they are facing, now they are getting merit from people about on how they have been consistent in their performance that is football things easily change.
We all still.belive that real Madrid is going to be doing a lot of surprises on people but for now the only people that we see leading now is Barcelona and that is all we see, so their is a lot that is about to happen. And I trust real Madrid so much also. When never can tell they might just do more wonders this season and if Barcelona should win is nothing new is not as if they have not won the la Liga before they are both each others rivals.