The two have met 23 times before Tottenham vs Manchester City on Saturday, Guardiola winning 11, Mourinho winning six, with six draws. Neither man has faced a rival manager more often.
But despite Mourinho's inferior record and his rollercoaster history of bust-ups and angry exits (Guardiola, by comparison, has never been sacked) one crucial factor makes Mourinho a far greater manager.
He has had to spectacularly overachieve at clubs in a way Guardiola has never had to.
Both have won the Champions League twice. But while Mourinho's victories came completely against the odds with Porto, then with a relatively unfancied Inter Milan, Guardiola's triumphs came with a Barcelona team that had Lionel Messi, Xavi, Andres Iniesta and co. in its squad when he took over.
As achievements, they are not comparable. Mourinho had to build himself up from a language translator and a nobody in the sport; Guardiola had the keys to Barcelona handed to him after a year coaching Barca B and a decorated playing career.
It would be ridiculous to deny Guardiola's coaching brilliance. He has got Barcelona, Bayern Munich and now Manchester City playing a dazzling style of trophy-winning football. In particular, the job he did transforming an underachieving Barca changed the way football was played.
But in terms of difficulty, Mourinho's tasks have been greater. Ever since his 2004 arrival at Roman Abramovich's Chelsea, "the special one" has been accused of crudely buying success. However it is Guardiola's track record that shows he managed one of the two richest clubs in Spain, followed by the richest club in Germany, followed by the richest club in England.
Mourinho - on the other hand - has had to follow the path of Sir Alex Ferguson or of Jurgen Klopp. He had to hugely upset the odds just to get a shot at managing a real super-club.
Translator, assistant coach, Uniao de Leiria manager, then Porto. The biggest club in Portugal, perhaps, but to win the UEFA Cup then the Champions League in back-to-back seasons is an achievement beyond anything on Guardiola's CV.
The pair have always been linked throughout their managerial careers. Mourinho allegedly wanted the Barcelona job when it was given to Guardiola, which caused the Portuguese to sour against his former employers (hard to imagine, right?).
It was another of Mourinho's great achievements - winning a Treble with Inter in 2009/10 - which split the two Champions League titles won by Guardiola's dazzling Barcelona.
Mourinho's Inter knocked out Barca in the semi-finals in 2010, a two-legged success widely seen as Jose's finest hour. Of course, in typical Mourinho fashion, he often sights the gutsy 1-0 defeat in Camp Nou as his side's greatest display, rather than the brilliantly executed 3-1 win of the first leg.
After that season, Mourinho arrived in Spain with Real Madrid and things got ugly. Fast. Guardiola won many battles - thrashing Real 5-0 a decade ago this month - but he was clearly worn down by Mourinho's constant desire to make it a deeply personal duel, between the managers, between the clubs.
At one point, an exasperated Guardiola ranted to the press about Mourinho being "the f**king boss, the f***king chief." Jose's constant mind games and media snipes had made it a battle of attrition.
In 2020, their relationship seems much better. Mourinho has mellowed (a bit). Also, his patchy record post-Real Madrid - some major trophies at Chelsea and Manchester United, but never sustained success - means they are not pushed into a head-to-hear war as they were in Spain. Probably to the relief of both.
Mourinho is aiming to rescue his reputation at Tottenham, the 57-year-old looking to prove he can work his magic in the modern game. Guardiola's status is relatively unblemished, Manchester City being only too eager to extend his contract to 2023. A Champions League victory without those Barca all-stars is probably the main, final thing Pep needs at club level to rubber-stamp his greatness.
But, unless something truly bizarre happens and Guardiola suddenly decides he wants to, say, take Benfica back to the summit of European football or to break the Celtic-Rangers in Scotland duopoly, Guardiola as a manager can never be quite what Mourinho is or Ferguson was.
Those managers had to beat the system, to work against stacked odds in order to join the ranks of super-coaches at Europe's elite clubs. Guardiola, on the other hand, has been playing with loaded dice from the start.
All imagery: PA Images
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