I think both teams are playing similar football at a very high level. Trying to say that one has been head and shoulders over the other when they have both had four easy wins doesn't wash especially when they beat two common opponents in similar fashion. Yes City win at Spurs but that Spurs midfield was a sieve, worse than the one that United faced days earlier. Conversely City, for all their better defending gave up two goals to the aforementioned piss poor Bolton. I also don't see how you can dismiss performances against a weak Arsenal/West Brom combination and then use Wigan and Swansea to tout City. Again my point is there is nothing in the opposition to say that City had a harder ride and the results are the same.
I still pick City as favorites for a couple reasons.
The first is Silva and Aguero. Both teams have been killing teams with good interplay among the front 4. Left sided players running through the center , on the right and up front. But if you compare the two Silva is running it much more than Young or Nani and he is more experienced. A lot of Young's game is pace and using open space and Nani has all the skill but is still learning.
Aguero for me is the biggest buy. Has the potential to do what Ronaldo and Henry did when they were in the league I.e. Win games singlehandedly over and over again. Rooney is playing the role that Aguero does but he has much more to do. Just like 2 years ago, for all his physical skills, it hard to see Rooney doing this all season. I think it will be interesting to see both of these teams play without these two players to make a better judgement of the teams' play.
I think the rest of the sides are even except that City's 1st choice midfield two Toure and De Jong are a better defensive shield than Anderson and Cleverley. Conversely the latter pair gives you more going forward. History says that a pair like Toure and De Jong wins you the big games but we will see.
I disagree that United have had had fewer contributors than City. I think United has just rotated their team less so far, nobody doubts that Park, valencia, Giggs, Carrick and Fletcher will perform. In fact even with very short minutes Giggs, Park and Carrick have all scored or assisted and that is addition to Anderson and Cleverley who, as a pair, have been in most of the goals.
As far as depth City is deeper up front. Chicarito and Dzeko is a wash, "just" goalscorers but City backup is Tevez and United's is Welbeck advantage City.
In defence I'll take Jones, Smalling, Evans and Fabio as backups over Zabaleta, Lescott, Savic and Kolarov.
In midfield both sides have similar quality backups but United has more bodies to come off the bench. City has Johnson, Barry and Milner as serious bench options but United still has Giggs, Park, Valencia, Carrick and Fletcher.