What are the key problems?
UNITED: The style of football, primarily. As Rene Meulensteen, Alex Ferguson's former first-team coach, said, United sides have an "obligation to entertain".
The risk-averse approach of Louis van Gaal runs counter to the traditions of a club immersed in a culture of vibrant attacking football.
The United manager will point out that his side will go to the top of the Premier League if they win at Leicester City today. But he is failing to recognise that winning alone is not enough at Old Trafford.
CITY: Injuries have played their part and the prolonged absence of Vincent Kompany has served to highlight the team's dependence on him. In 10 games with their captain, City have conceded three goals and kept seven clean sheets.
In as many matches without the centre-back marshalling an otherwise unconvincing rearguard, they have shipped 17 goals.
Yet, City's infuriating inconsistency hints at a more serious flaw running through the side. They also possess an inferiority complex when it comes to big European matches.
Is the manager part of the problem?
UNITED: Van Gaal effectively sets up with six men behind the ball, with two central midfielders asked to sit deep and the full-backs kept on a tight leash. Creativity is stifled and the lack of runners from midfield is pronounced. It is an ultra-defensive formula that the Dutchman believes offers the best chance of delivering the title.
It is not uncommon for van Gaal to rebuke individual players in front of the whole group as he picks over mistakes during long, laborious video sessions put together by Max Reckers, the performance analyst. Yet, whereas David Moyes never won the respect of the dressing room, the players know their place under van Gaal.
CITY: Manuel Pellegrini has shown signs of getting tougher with his players. But just when it looks as though he is allying a pragmatic streak with his squad's attacking flair by deploying a three-man midfield, he reverts to type.
City's line-up in the 4-1 league defeat by Liverpool last Saturday was bewildering in its naivety.
Which players have been the most disappointing?
UNITED: Wayne Rooney is in an awkward place. Van Gaal has put great faith in him, yet the captain is concerned that the team are being undermined by the manager's tactical straitjacket. Those close to Rooney would point out that he has scored 11 goals in his past 11 starts for England, a team playing with more freedom. Matteo Darmian, after an encouraging start, and Memphis Depay have been disappointing for United, but many players are hampered more by the suffocating system in which they are being asked to operate.
CITY: Pellegrini has spent £74 million (S$157 million) over the past two summers trying to find a pedigree partner in defence for Kompany, but Eliaquim Mangala and Nicolas Otamendi remain liabilities.
Yaya Toure no longer seems able to perform in a midfield two and they are weak in the full-back positions.
THE TIMES, LONDON