Goal keepers is an interesting one. De Gea is new and adapting, he's also younger and in the middle of a culture change, that all said, he's been the best keeper in the league for the second half of the season and it probably the best keeper in the league for playing out and also shot stopping. His potential is just ridiculous. But right now I'd choose Hart. Just. (even though De Gea has won more.)
I'd definitely take Ferdinand and Vidic over any of their defenders, as good as Kompany is. Given age is going against Ferdinand, from next season I'd maybe change that, but whilst people are raving about Evans, it's Ferdinand that has shored up our defence so much since his return. He blocks strikers fouling our keeper from set pieces, he orchestrates so many attacks, cuts out trouble and covers for Evra who continually gets beaten down the byline. He has also been phenomenally important in giving Evans the confidence to play a bit.
A fit Vidic I'd take over any other centre half on the planet.
Where City are stronger is Richards is more accomplished than Rafael. Rafael is better playing with the ball, but Richards is a force and when he wants to, he can be mean to play against.
Evra has been pretty poor this season and the fact he doesn't score or assist anywhere near the numbers he should really do count against him, but he's still a better player than all of City's left back options overall, though Kolorov is always a threat coming forward (and with set-pieces)
City have an issue with wide players, Man Utd depend heavily on two (Young and Valencia) and struggle on with another (Nani), City only really offer true width with Adam Johnson. They do play Nasri, but all too often he's anonymous and he really hasn't had a good season, nor has he ever really done anything to warrant a status. I'd take him over Nani, but really, I wouldn't be in a rush to have him either.
They also insist on playing Barry who really is just a very poor version of Michael Carrick. He doesn't read the game as well, doesn't pass as well, nor protects his defence as well. He should be the first player they replace.
Man City are strong in midfield with Yaya Toure, but without him they continually struggle. Their faults started to come when he left to go with Ivory Coast at the start of the year and they collapsed completely in midfield when he came off injured.
Silva has faded so much it's scary, but he can unlock defences, he's a high line ball player and something Man Utd need, but there aren't many around.
Carrick, Scholes, Anderson, Giggs and Park have shown time and again they have what it takes to come in, do a job and win titles. All of them have won a Champions League and numerous Premier Leagues, so I'd have to say, bar Toure and Silva, United have a more solid, cohesive selection of midfielders.
In other positions they are stronger. I think it's probably a toss up between Aguero and Rooney, but Rooney is talismanic, Aguero isn't.
In the other options their stronger. Hernandez is probably the best sniffer and Berbatov is the most technical, but Tevez is a beast when he wants to play, but has attitude problems. People make more of Balotelli than he's ever shown, he hasn't really done anything in 4 years now of mainstream football bar the odd flash of brilliance, he's a loose cannon on and off the pitch. Dzeko started well but faded, but can be solid. Overall their other options are definitely stronger than United's though.
And then there's Ferguson.