If we look at the Atletico Madrid - Manchester United matchup, we can say that it is going to be a very competitive matchup for sure. Because I don't see a big difference between these teams now. Maybe Atletico Madrid's form lately hasn't been better than Manchester United. But if we take their general performances into account, it is more visible that they are close to each other. If I'm to favour one of them, my choice would be Manchester United.
Those who think Atletico Madrid are going to lose to Man Utd because Ronaldo has 4 hattricks against them and are in for a huge disappointment. Man Utd were Premier League Champions for decades, now a decade is almost gone without a single league title, This is the beauty of football. Things change. Nobody ever thought Barcelona would come crashing down, high flying Barcelona are now in Europa League, and you think Cristiano will bail Man Utd out once again because of history? He's going to fail spectarcularly.
If you think because Manchester United has not lifted a league title for about a decade will make ATM win Manchester United, I think it's also not a good analysis. In football, you cannot do without history. If you can check Manchester United vs ATM h2h better. Then Ronaldo has an incredible individual stat against ATM and will be in Manchester United team. Currently, Manchester United has gone 4matches unbeaten which is directly opposite to what is happening to ATM now. So?