Tier 1
City, PSG, Bayern
Tier 2
United, Liverpool, Chelsea
Tier 3
Madrid, Juventus, Atletico
Tier 4
Barca, Dortmund, Atalanta
United should definitely be up there with Bayern.
Bayern have lost a lot of quality in central defense with Alaba and Boateng leaving, with only Upamecano joining in.
They also lack numbers in that area. In CB they only have Hernandez, Upamecano and Sule, while Nianzou is still very raw to be considered a quality option. Pavard can be called on but he's their first choice RB and therefore they then will suffer there.
Similar for LB, where Hernandez is likely their secondary option, though they signed Richards, who is again unproven at this level. Once again they are relying on a couple of players to convert multiple positions.
This isn't an issue at United as we have a clear list of 2 good players to cover at each position. Shaw and Telles at LB is certainly better than Davies and Richards, while AwB and Dalot are also better than Pavard and Sarr (who has been terrible for them).
CM and ST is where Bayern can come out on top but that's only because of their starting XI. If you compare squad depth, you'll again find that United have a stronger bench with McTom, Matic, Mata, VdB, Lingard compared to Tolisso (chronically injured), Cuisane (who Bayern want to rid off), Roca (who barely played last season) and Musiala.
Bayern are terribly lacking in bench strength and that was evident when they lost to PSG with a string of injuries. They haven't been able to strengthen that bench due to Covid and therefore for this season again they'll have to reply mostly in their starting XI to win them matches.