Manchester City are stronger and are a favorite team to win but Manchester United have good players. They are not as strong as Manchester City, lack of stability but in a single match, they already shown that they can beat big clubs in Premier League. With Manchester United and their instability, it's hard to predict their performance in big matches. Sometimes they do good, win in surprise of all but other times they play very poorly and got big defeats surprisingly too.
Latest forms of two teams are opposite and Manchester City are performing better and they probably will get three points from Manchester United in Manchester derby.
Manchester City have much greater motivation because they are in the competition for the Premier League title this season and also Manchester City will play at their own pace, with Manchester City's performance being quite good at the moment after the return of several main players from injury of course making Manchester City will be quite the favorite to win the Manchester Derby match, especially since Manchester United this season has not been able to consistently maintain its best performance.
However, in big matches surprises are possible and this is also a Derby match that is full of prestige so Manchester United will give all their strength for this prestigious match.
I think it is not impossible that Manchester United will be an obstacle for Manchester City in the title race this season because in terms of overall strength Manchester is not that bad.