Apart from the sheer accumulation of top honours, both clubs have been led by some of the greatest managers in the history of football. And some of them stayed and stayed and won and won.
None more than two of the greats at United, the true Red Knights, Sir Matt and Sir Alex. Between them, they have occupied 50 of the 66 years since 1945. And between them, they have won 50 major trophies.
For comparison, Bill Shankly and Bob Paisley won 31 major trophies. Nobody else comes close.
So it's not difficult to imagine who the top two post-war managers are for United. There are only six others, so we don't even have a top 10.
The last 66 years have not been all glory at Old Trafford. There has been heartache, heartbreak, glory and mediocrity. Throughout this modern era, the fans have stayed true, buoyed by a consistent style of football that may not always have produced results but has always pleased the eye.
Sir Matt created a footballing dynasty from the rubble of a war-ravaged club. He was still "upstairs" when Sir Alex arrived. The period between sandwiched some indifferent episodes conducted by average management and an array of styles.
Here we rank the eight incumbents during an epoch and an evolution that have stamped the character of Manchester United indelibly for all of our lives. Some were great, some colourful and some, frankly awful. All tried to fly the flag for football and carry the torch first lit by Sir Matt Busby.
When Sir Alex Ferguson finally retires, who on earth is going to follow the greatest manager of all time?
That was pretty much the dilemma that the Manchester United Board faced in 1969 when Sir Matt Busby stepped down after 24 years as manager, ending the most successful period up to then in their history.
They can't be blamed for taking a route that Liverpool pretty much followed through their later period of glory, by appointing from within. And the man they chose had most of the right credentials. The trouble was, it was a bit like appointing Gary Neville to follow Sir Alex.
Wilf McGuinness had occupied almost every role in Old Trafford. He came up through the youth team as one of the "Busby Babes"; he played in that great team and would have been on the plane but for a broken leg; his career finished early and he had been a coach and assistant manager to Sir Matt. He knew all the players, so who could blame the Board for his selection?
He had also played for England at every level and had trained, coached and managed their under-18 and under-23 teams. He was even on Sir Alf Ramsey's management team at the 1966 World Cup.
But he himself would say that managing United came too soon and was a step too far. He had managed the reserve team, sure, but he had grown up or played with many of the lads and now he had to train them and pick them and he couldn't make the transition.
He also inherited the growing challenges of managing George Best. Even Sir Matt struggled with that, especially in his second term. And Sir Matt was still around. We shall never know whether or how Wilf was left to his own devices.
But he couldn't begin to emulate the great man. Sure, he took the team to three semifinals but only survived for 18 months before the inevitable axe rescued him.
He escaped to Greece to manage before he eventually arrived back in England at his final managerial post with York City. Even there, he took a side that had just achieved its highest-ever league position through two relegations to the point where they had to apply for re-election.
Irrespective, Wilf McGuinness had the humility to return to Manchester where he has throughout his life been a great and very personal ambassador for the club he loves.
Frank O' Farrell was also caught in the tailwind of Sir Matt's retirement. To give an insight into how difficult it was for both him and Wilf McGuinness, after Wilf went Sir Matt had stepped back into the breach for six months, so Frank had to follow the great Scot also.
The key difference from Wilf, however, was that Frank was an established manager. His main appeal was that he was regarded as a talented, young manager heading into the future.
He had been successful to be sure, guiding three separate teams to win their leagues, but these were Weymouth in the Southern League, Torquay in the Fourth Division and Leicester City in the Second. But it was a bit like appointing Phil Parkinson to succeed Sir Alex—no European experience, no major trophies, no idea about managing in the top flight!
Frank also lasted only 18 months. His detached, unapproachable management style didn't work with the players—and especially George Best.
Thanks to Sir Matt, he took over a club which won the European Cup only three years before. He started well and United were 10 points clear at the top at one time. But there was a rapid downturn, they finished eight and with a poor start the following season, he was sacked halfway through the season.
Despite so many players having grown old together, it is hard to conceive of how quickly United had collapsed after their first European Cup triumph.
A strong, successful, self-confident manager was needed to turn the tide...
Some might have Tommy Docherty higher in this rankings list because he did at least win the FA Cup. But there are at least two compelling reasons for keeping him at No. 6: the tawdry circumstances of his sacking, which brought damaging publicity to the club; and getting United relegated for the first and last time since 1938.
Oh, and for getting rid of Denis Law to City...
"The Doc" had already been successful at Chelsea. Taking over in his early 30s, like Wilf McGuinness at United, Tommy couldn't save the Blues from being relegated but took them straight back up as champions and to fifth place in the First Division the following season. They won the League Cup in 1964/5. He was a talent spotter and had signed some exciting players at Chelsea.
His beginnings at United were almost a carbon copy of his Chelsea experience. He failed to turn around a struggling side and in his second season they were relegated. Taking them back up as Second Division Champions, he then took them to third place in the top tier.
Like Sir Alex, he was a tough Glaswegian and had even been Scottish manager before arriving at United. But this was the period of Liverpool's greatest glory and, unlike Sir Alex, The Doc couldn't knock them off their perch.
His win percentage was better than that of any other post-war United manager except the two Scottish Knights and Ron Atkinson, at 47 percent, but a pale shadow of the club at its best.
Dave Sexton may not have had as good a win percentage as Tommy Docherty, but he was an excellent coach. He also succeeded Tommy at both Chelsea and United.
At Stamford Bridge, he won both the FA Cup and the European Cup-Winners Cup. He then went on to the unfashionable Queens Park Rangers, who had not long before come up from the Southern League. But if not for a last minute win by Liverpool, Rangers would have won the First Division.
Not surprisingly, United snapped him up after the Docherty debacle. But he was also a "nearly man." The club and the team were going through a difficult time. Sexton didn't have the flair players he had at Chelsea. It was a period of transition and recovery following the shocking decline after 1968.
United were losing Cup Finalists in 1979 and pipped by Liverpool in the League in 1980. But the football was dour and uncharacteristic of the club that Sir Matt had reinvented after the war.
He did sign Ray Wilkins and Joe Jordan and actually won his last seven games in charge, but he also was suffering from being in Liverpool's shadow and second best wasn't good enough. After four years without a trophy, he too was sacked.
Some people might ask, what Jimmy Murphy is doing on this list?
He was acting manager while Sir Matt was recovering from the Munich Air Crash. In many ways he saved the club from ruin during that period. Reluctantly he took over the club and even got them to a Wembley Cup Final.
He had been responsible for grooming and coaching many of the Busby Babes and was a hugely effective motivator. Bill Foulkes was mentally shattered after the disaster but Murphy instructed him to be captain.
He was also responsible for pressing Les Olive as club secretary after Walter Crickmer had died.
With so many talented, young footballers dead and a fixture list to fulfill, Murphy begged and borrowed players to add to the residue of the squad and United finished ninth, which was extraordinary. Indeed, they might well have won the Cup as well but for a dreadful assault on Ray Wood, that left United without a goalkeeper.
So, he makes No. 4 for his lasting legacy that kept the Busby era going under the most trying circumstances.
In terms of statistics, Ron Atkinson is the third most successful manager of United since the war, ironically not far behind Sir Matt, but well ahead of the other disappointments, with the near exception of "the Doc," who unfortunately blotted his copybook.
Big Ron was certainly colourful, dripping with gold bracelets and watches, dark glasses and all.
He had made his name at West Bromwich Albion where he became the first manager to field three black players in the Football League.
He led WBA to third place in 1979 and fourth in 1981. A 5-3 win at Old Trafford helped his cause and, after Dave Sexton was sacked, he was a sensible choice.
Under Big Ron, the fans began to think the good times were back. United finished no worse than fourth place in any of his seasons in charge. He also took them to Wembley three times and his two FA Cup wins made him the most successful manager since Busby.
He brought Bryan Robson, Gordon Strachan and Frank Stapleton to the club and developed Mark Hughes, Norman Whiteside and Paul McGrath. But despite his relative success, a disappointing start to the 1986/7 season and the growing appeal of Alex Ferguson ultimately led to his demise.
Along with Tommy Docherty, Ron was one of the more memorable and most popular managers, with a 50 percent win percentage.
Ernest Mangnall was United's most successful manager ever before Sir Matt, winning the first two league titles. He is also the only person to manage United and City and is credited with moving the first to Old Trafford and City to Maine Road.
After the disruption of the war years and a drought of 40 years, Sir Matt was undoubtedly the father of the modern United era. Sir Alex has also credited him as a mentor.
It would be difficult to place him ahead of Sir Alex, despite his achievements. Both have served the club for about 25 years; both have a track record of developing youth; and Sir Matt was as responsible as anyone for the style of football that United have played ever since.
He was indeed one of the greatest managers of all time, ranking alongside Bill Shankly and Bob Paisley at Liverpool. He will never be forgotten, and not just because his statue adorns the front of the stadium.
No doubt, one day it will be joined by a bronze memorial for Sir Alex.
This is a great man and a great manager.
From humble beginnings in Govan, the son of a shipyard worker, Ferguson worked in the yards himself while playing football.
He went on to play for Rangers as a centre forward. After finishing his playing career, he managed East Stirling and St. Mirren before making his name at Aberdeen, where he broke the "Old Firm" monopoly and won the European Cup-Winners Cup, beating Bayern Munich and Real Madrid in the process.
In all, he won 10 major trophies with Aberdeen, including three League titles and four consecutive Scottish Cups.
He had been approached by Arsenal, Spurs and Wolves before accepting the United job. It is well known that he was believed to be on the verge of the sack before Mark Robins scored the winning goal against Notts Forest in the FA Cup in 1989/90.
United went on to win the FA Cup that season and Fergie never looked back. It later emerged that the Board was never looking to sack him, but that didn't stop it from being his darkest period as a manager.
He finally won a title in 1993, almost seven years after he had arrived.
To have won a total of 12 titles in 19 seasons and a total of 37 major trophies in less than 25 years is extraordinary in itself. To still have the same fire and determination, passion for the club and will to win in his 70th year is astonishing.
He has truly carried the torch first lit by Sir Matt and is the arguably the greatest living manager, if not the greatest of all time.