El Clasico is always an important match for both teams because it has been a prestigious match for both teams for a long time, but currently both teams are in different conditions, Barcelona is in a downturn after being eliminated from the UCL and this is inversely proportional to Real Madrid which makes them now is in high self-confidence.
This is an important match so there is no reason for both teams not to field their main squad, both teams are aiming for victory with different motivations.
I hope Real Madrid win, because they will be closer to winning the league. Maybe they're in a different mental state now. Real Madrid are in good form because they've qualified for the UCL semi-finals. Unlike Barcelona, they lost badly at home and it's something they need to work on mentally and in their game. Besides, Real Madrid will be playing at home. They have a huge support, so the Barcelona players might be under pressure from the fans. Maybe Madrid can win 2-0.

On the one hand, Real Madrid is mentally more tired, and since it is in the Champions League, we also need to add physical fatigue. However, I don't think it will affect Real Madrid players and if they beat Barcelona today, they will at least be able to relax in the league. No matter who wins, I hope to watch an enjoyable and passionate El-Clasico tonight, I hope both teams don't lock each other and it will be a fluid game.
This feeling motivates Real Madrid more because they are home, and also the players of Real Madrid, as they are closer to their goals than Barcelona, even though they are busier and more physically tired. They have better players and a game plan, so there is no reason why they shouldn't win.