I'm sure it will be Barca with Lamine extraordinary performance, as for Real Madrid, They have a bunch of stars but I feel they aren't gonna coorperate and they wont be good chemistry among them.
Ancellotti is very good when it comes to man management. All his career he has managed stars. In fact, when we talk of a star studded teams, this current Madrid is not among the best teams he has managed. Players he has coached in the past also said he was good at man management. I don't expect dispute to be in Real Madrid next season, in fact I believe it's when Ancellotti leaves that the team will have issues.
Players like Vinicius owe their current form to Ancellotti. Before Ancellotti, Vini wasn't this good before Ancellotti and we can also see how he brings out the best in Bellingham, something his other manager (Southgate) can't.
Barcelona might be very good next season (a very big if), they might win the league, but it won't because of trouble in Madrid.