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.