Neither of clubs have advantage. We know how crap City is. They're terrible in all of lines, but same things are happening with Madrid too.
Although, Real Madrid is in a better state than City, they're mentally better in domestic, but they're also bad in UCL. If i should chose, i'd i pick Madrid. The problem is the risk is quite high.
I decide not even pick any of them. In this case, betting on BTTS most likely become the profitable bet. I'm pretty sure the game ended with narrow score like 2-1 or 3-2 Madrid win.
It is difficult to bet on who will win in the Man City vs Real Madrid match, because both teams have different moments and both teams had the same fate last week in the domestic league, both lost. Maybe betting on over 3 goals in this match would be better than betting on which team will win.
Mentally, Real Madrid is indeed superior to Man City. But the problem is, before facing the Champions League, both teams have different rest times and will face teams with different qualities.
Man city only has one match before facing real madrid, namely they have one FA cup match against leyton while real madrid will face two matches before facing man city, namely against lagens in the copa del rey and atletico madrid in laliga. Of course this will drain the energy of real amdrid players, especially Rudiger is certain to be absent when facing man city due to injury.
So with this consideration both teams have the same chance of winning.