Manchester City is strong but I think you are not giving Chelsea enough credit. Manchester City has good team but they have some weaknesses in defense and midfield that Chelsea could take advantage from. Chelsea has been playing well recently and they will probably give Manchester City hard time. I agree that both teams will score goals but it is hard to say who will win. Chelsea might be able to use Manchester City weaknesses to get tie or even win game. Match is going to be exciting and very competitive.
Based on Manchester City's performance in today's match, it seems that Chelsea will be able to put on a stronger performance than them. If you judge by their current match performance, Chelsea and Manchester City are definitely equal ahead. Yes manchester city was good team but they are weak in defense, midfield and attack maybe chelsea will be able to play much better against manchester city with this opportunity. However, Chelsea and Manchester City's head to head record match results show that Chelsea never won against Manchester City. So it may still be doubtful which team will actually be able to win this match.