Over the long term, the paths taken by the two clubs have been very different. That is evident both on the pitch in tactical terms and in their squad-building strategies, including the emphasis they place on local identity. Most factors point to contrasting, and sometimes even diametrically opposed, approaches.
The same is true this season and of the styles adopted by Hansi Flick and Jose Mourinho, two coaches of a similar age.
The former leads Barcelona in the tradition of attacking and attractive football, both with and without the ball: "I think we're talking about the best attack in Europe this season. On the other hand, there are still defensive problems," says Flashscore data specialist Marek Kabat.
In Madrid, he believes Mourinho's appointment has taken the club down the route of defending in a mid-block and relying on counter-attacks: "The question is whether a club like Real, with that level of quality and such a standing in world football, should develop in this direction over the long term. For now, though, the season is showing that Mourinho has been more successful with it than expected," Kabat notes.
Real won El Clasico, but Barca lead the league by three points. Their average xG per game in the domestic competition is almost three goals, the highest in Europe, ahead of Bayern and PSG.
Their rivals, by contrast, are getting used to playing without the ball.
"Under Ancelotti, average possession was 61%; under Xabi Alonso, it was 64%, and now under Mourinho it is around 51.5%," Kabat says. He has also noticed the large volume of opposition attacks taking place in Real's defensive third: "I can't imagine them coping with that in a match against PSG or similar teams."
He sees Barcelona's defence as a strength, even though the team allows opponents counter-attacking chances worth 0.6 xG per game, more than last season (0.54).
"I think Rodri was supposed to be the one to help solve that. You can see that he is key to the rest of the defence. He has made the most interceptions, and his positional play is fantastic, but evidently it is not enough."
The Catalans are also currently short of a centre-back - or rather, two: "In the summer, they should have signed Alessandro Bastoni rather than Anthony Gordon," he argues.
One major success of Real's new style under Mourinho is how effective they've been in combining a mid-block with counter-attacks.
"Even though they are not as dominant in matches, they are capable of being very effective at creating chances. At the other end, they and Atletico have the lowest xG conceded per game," Kabat points out.
He also highlights the mental aspect the new coach has brought to the team: "To me, it is obvious that things have improved in the dressing room. That is something Mourinho has always been good at - psychology, motivating players…"
The two sides also use different formations.
On paper, Barcelona line up in a 4-3-3, but that usually becomes a 3-2-5 in possession. High pressing is a major part of the team's game.
"It always starts with the forward. Barcelona could not have a player there who is unable or unwilling to do it. I was surprised that the coach solved the centre-forward position with Raphinha, who handles it fantastically," the analyst says.
Real most often line up in a 4-2-3-1. When defending, they switch to a 4-4-2 or even a 4-4-1-1 in a mid-block.
"In terms of the underlying principles, the biggest changes concern the midfield setup and the right-back. That position is very interesting because Federico Valverde often operates there. Although he plays in central midfield, he is able to drop back alongside the centre-backs," Kabat explains.
In the recent El Clasico, Real won 2-1 at Camp Nou, but Kabat feels that a draw would have been a fairer result.
"Barcelona had 18 shots, but they were worth just 0.07 xG per shot, which is below their average. Real, meanwhile, had 10 shots in total, six of them from inside the box, and therefore with a high xG.
"Their greatest achievement was neutralising Barca's attack. I was surprised by just how successfully they managed it."
With the cores of both teams made up of very young players, a long period of fascinating battles lies ahead.