United don't have a "very good" squad...wtf. It is so $#@!ing unbalanced. They've spent a lot of money on trash. Their defence is laughable, their midfield is still $#@! *even though they thought they rectified it beginning of the season) and their attack is still a joke. So much so that they really on fat old Rooney to still score goals for them.
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Most of their fans want Woodward out on his ass, after they've spend close to 250M on mostly un-needed rubbish players. Chelsea definitely have a stronger squad, and their reasons for failing have nothing to do with their quality.
I am not going to praise their management. How they handled di maria alone is criminal but they have about as good a squad as Chelsea's if not slightly better.
UTD has better strikers while Chelsea has a better midfield. Both have serious issues at the back with UTD having a slight advantage there. More importantly, Chelsea are more broken mentally and will have less money to spend.
Strikers: Rooney+Martial > Costa, Pato?
Wingers: Valencia, Depay, Young, Lingard << Willian, Pedro , Hazard, hopefully cuadrado
AMs: Mata > Oscar
CM/DMs: Schweini, Scheniderlin, Carrick, Fellaini, Herrera > Matic + Fabregas + Mikel
CB: Blind, Rojo, Jones, Smalling > Zouma, Cahil, Ivanovic? (Terry is gone)
RB/LB: Darmian, Luke shaw > Azpilicueta, Ivanovic
United has (1) a larger squad(substantially more depth), (2) slightly better players in most departments, (3) much more money, (4) in better mental shape than Chelsea, (5) has much more patient management than Chelsea. They also have a bigger brand in football but that will be trumped by money. Its the easier job.
I gave you 5 reasons for why I think United is the easier job. Hiddink who is a top level coach have not managed to get them anywhere near their level. Mourinho (arguably one of the best coaches of all time) flopped with this group of players. This is how broken mentally they are.