At first glance, there are more similarities than differences. They are the two biggest clubs in Spain, are supported by hundreds of millions of global fans, employ the game's biggest stars, have the biggest budgets in football, and monopolize Spanish League titles.
They are two institutions locked in an eternal death hold of obsessively benchmarking themselves against the other. One cannot be up without the other being down. Football, goals, victories, and even titles become subservient to the unquenchable thirst for superiority over the arch rival.
Thus it has always been for Real Madrid and Barcelona.
Yet, in spite of the many ways that the clubs mirror each other, there are fundamental differences to how they approach the game of football. These differences were made clear in Saturday's Clásico, and Barcelona's model ran out winner.
The first and most obvious difference between the clubs is the approach taken to building a squad.
Real Madrid's record-shattering summer expenditure was another example of the transfer policy Madrid has pursued for the last decade. The best players in the world are signed, regardless of their price. They spent €300 million to bring in another wave of established international superstars. Out went the majority of the Dutch contingent that, along with Fabio Cannavaro, had been the backbone of the side's last two titles.
Unsurprisingly for a side that is constructed using the president's checkbook, only two of Madrid's starters are former youth academy players. The contrast with Barcelona is stark. Seven of Barcelona's starting 11 are from the academy.
This is not accidental. Barcelona have one of the best youth academies anywhere, and they construct the first team around the academy graduates. The players signed from elsewhere are brought in as complements to the players developed in-house.
The second difference is the style of play, and its role in achieving results.
Barcelona have played in the same style since the arrival of Johan Cruyff as coach in 1988. The 3-4-3 he used has been modified over time, but the use of wide forwards and the attack based on possession are sacrosanct.
Four of the seven Barcelona managers that followed Cruyff have either played under him or came from Ajax, the other perpetrator of the style. The late Sir Bobby Robson won three titles in his only season at Barça, but was hounded out for changing to a counter-attacking style.
Barcelona's academy grooms young players in this philosophy of play from an early age, which allows them to make the transition to first team football with unusual grace. Busquets and Pedro, are perfect examples of this. The pair were plying their trade in the fourth division just two years ago. Now they have displaced Thierry Henry and Touré Yayá from the starting lineup and may find themselves in South Africa this summer.
At Real Madrid, style is important, but ultimately secondary. Victory is the highest aspiration of the Bernabeu faithful. Twice in recent years the famously-defensive Fabio Capello was brought in return them to winning ways. He was never loved, but accepted as a necessary measure to assure titles.
Formations and playing style are, like at most clubs, seen as a means to an end. Different coaches are free to impose their own playing style on the players, with the only condition being that it bring results.
On Saturday, the teams were true to their history. Barcelona set out to control possession and open the field with their wide forwards. Madrid set out to disrupt the visitors by pressuring them all over the field.
Madrid were largely successful for the first half, and Barcelona struggled to establish a rhythm. When Madrid recovered the ball they moved it forward quickly to Cristiano Ronaldo to strike on the counter. They had more shots than the visitors, but few of them truly threatening.
As time wore on, Barcelona began to impose their rhythm on the game and deprive Madrid of the ball. Two perfectly weighted through balls from Xavi put Barcelona up 2-0, although it could have been 4-0 with a Messi hat trick had Casillas not intervened majestically.
In truth, the way this game was won suggested that Barcelona's superiority would translate into a similar result however many times the game is repeated.
For a club that prides itself so much on achieving results, the loss will be tough for Madrid to take. There is now a ticking time bomb under Manuel Pelligrini's chair. Coaches are always the scapegoat for a team's failure, but in Madrid this is taken to extremes. He looks very likely become the 19th manager fired in 19 years.
The press is already composing shortlists of possible successors. Unsurprisingly, Mourinho and Benitez are at the top. Whoever it is, he will likely be joined by another "Galactico" to add to the constellation of stars in the capital.
Yet, given the excellence that their rivals have achieved with institutional stability and tactical coherence, perhaps more knee-jerk reactions are exactly what Madrid doesn't need.