They're playing in a superior system and most of those have a 'consistent' bottom level, not to mention your players are in better form but in terms of very high upper level of performance where they can be breathtakingly good... Hazard is obviously head and shoulders above everyone but I don't think many of your players are say World XI level, or EPL XI for that matter.
De Gea > Kepa
Valencia/Young < Azpi (more solid defensively but going forwards, Valencia offers more in build up)
Bailly > Rudiger (Rudiger is performing much better this season though)
Smalling = Luiz (Smalling is better defensively but Luiz better on ball)
Shaw < Alonso
Matic > Jorginho (Matic at his peak is better player)
Pogba > Kovacic
Mata/Herrera < Kante
Martial > Willian/Pedro
Lukaku > Morata/Giroud
Rashford/Sanchez < Hazard
First team wise.. its pretty much even, but I just think United have more talent in those forward areas, more varied attack whereas you guys are heavily reliant on Hazard for chance creation. I can't see Willian and Pedro winning games or being the main thorn in an opposition like Martial can do at his best, Morata and Giroud aren't much of a goal threat and Pogba will impact games more than Kovacic.