One group has been together five years, largely assembled through world-record fees. They live in a perpetual goldfish bowl of endorsements, global tours and branding, much of it dutifully chronicled on social media. They are the established act, the aging rockers on their umpteenth victory tour, and no matter if, for this last performance, one or maybe even two of them might make way for a backing artist.
They remain the "BBC" -- Gareth Bale, Karim Benzema and Cristiano Ronaldo -- and they're the blunt attacking force that could turn Real Madrid into European champions for the fourth time in five years. It's something nobody has achieved since, well, Madrid themselves more than half a century ago.
The other is a rising boy band who few would have even conceived of when the "BBC" supergroup was assembled five years ago. Sadio Mane was in Austria and had yet to see a minute of European football. Roberto Firmino was playing in midfield for Hoffenheim. And Mohamed Salah, the last piece of the puzzle, had finished his first season in Europe, at Basel, mostly coming off the bench. There's no catchy acronym, but you'll find plenty of the "heavy metal football" their coach, Jurgen Klopp, craves.
These two attacking forces are set for a showdown in the Champions League final when Real Madrid take on Liverpool, the Establishment vs. the Upstarts.
With these men, it's not just about where they are; it's about where they come from. Real Madrid's trio are all blue bloods who were tipped for greatness before they turned 20. Bale moved to Tottenham Hotspur at 18 for $10 million back when that was still a lot of money. Benzema had been capped by France and was the crown jewel at Olympique Lyonnais. Ronaldo was the apple of Sir Alex Ferguson's eye in Manchester United's Theatre of Dreams.
As for Liverpool's trio, when they were still teenagers? Mane was at Metz in the French second division, where he scored a single goal in 19 games. Firmino was at Figueirense, helping them earn promotion to the Brazil top flight. Salah? He had made his first appearances for Egypt's El Mokawloon but hadn't been playing much at all since the Port Said tragedy in 2012 brought the league to a halt.
Yet even pedigree must succumb to the passage of time. In terms of the BBC, this has been the toughest season yet. Bale, beset by injuries, missed chunks of the past two seasons and was dropped for the Champions League final last year. Benzema, once considered untouchable as the workhorse who made those around them look good -- and sometimes to the chagrin of purists who judged him solely by his goals total -- is by no means an automatic choice. He hasn't played 90 minutes of a Champions League game in more than two seasons.
Bale and Benzema's roles as Ronaldo's complements have diminished, too, as Ronaldo himself has changed with age. He's not the fleet-footed wide man he once was, picking up the ball deep and mazily dribbling his way into the heart of the opposition defence. He is, essentially, a centre-forward who gravitates to the left. There is now a minimalist efficiency to his game; no ounce of energy wasted, everything geared towards scoring. This has allowed him to maintain his goal production even into his mid-30s, giving Real Madrid a forward reference point and, in that sense, making Benzema somewhat less indispensable.
They've all had to adapt. Benzema has to adjust his game to the areas Ronaldo now occupies with greater frequency, and Bale can't simply be the right-flank photo-negative yin to Ronaldo's yang. With Zinedine Zidane having a wealth of forward options beyond the trio, from the playmaking Isco to the explosive Marco Asensio, Bale, Benzema and Ronaldo can no longer be the three divas with a backing orchestra of eight guys. They have to tailor their game to the symphony.
Liverpool's front three are far more choreographed in terms of movement. Salah might have scored the most goals, but he is not the main terminus: he's a cog in a harmonious trio where no part seems to operate independently of the other two. Firmino is the nominal centre-forward whose movements left or right cue Salah and Mane, and vice versa.
These aren't three individuals, either, as the BBC can sometimes appear. This is a collective of three men with slightly different skill sets (albeit with a common theme of flat-out, gut-busting work), whereby Firmino's altruism and vision, Mane's quickness and trickery, and Salah's finishing and speed combine for devastating effect.
The BBC have already made history. Now they hope they can conjure up one last masterclass performance, even though for two of them (Benzema and Bale) it's not even guaranteed they will be in Zidane's starting XI on Saturday or beyond this season. The Champions League final will determine whether their chamber music, perhaps with the help of a few stand-ins, can withstand the "heavy metal" of the upstarts in red who play louder and faster than they do.