Honestly, I don't expect Barcelona to win the El Clasico. Above all else, I think that Barcelona's first target will be to win against Inter in the Champions League. Because after that unexpected loss against Inter last, they are three points behind them in the group. If they lose points again they might really find themselves in the Europa League two times in a row. This would be really a mockery for most people. 
I feel like Real Madrid won't lose in Santiago Bernabeu to them no matter what kind of a result Barcelona get against Inter. I expect Barcelona players to be quite fatigued after the Inter game. I don't expect the same from Real Madrid players against Shakhtar because they are already in a safe condition in the lead. I don't think Ancelotti would like to wear out his players too much right before the El Clasico. I'd just prefer to add both teams to score to my parlay and enjoy the El Clasico.
Real Madrid odds are slightly better than Barcelona. Their games in Champions League require more effort from Barcelona's players comparing to Real Madrid's one. Yet everything could happen obviously. I find Barcelona better but sometimes the concentration level is a bit lower which leads to disasters like what happened in Inter's match. Now in the next game vs Inter, it will be bad if Barcelona lose again.I feel like Real Madrid won't lose in Santiago Bernabeu to them no matter what kind of a result Barcelona get against Inter. I expect Barcelona players to be quite fatigued after the Inter game. I don't expect the same from Real Madrid players against Shakhtar because they are already in a safe condition in the lead. I don't think Ancelotti would like to wear out his players too much right before the El Clasico. I'd just prefer to add both teams to score to my parlay and enjoy the El Clasico.
After 8 rounds in La Liga, Barcelona received only 1 goal at the opposite of CL where they received 4 in 3 games.