I'm tempted to agree with you, but it's not a certainty. We won the last game against them. And we've beaten them a few times before in the last 5 years.
Even though City are a much, much better team than us, they just happen to be vulnerable on the break, because they play such a high line in possession. And by sheer coincidence, that is literally the only type of football we can play somewhat decently. So City aren't tactically our worst type of opponents to play against, although they are technically a nightmare for us in most matches unless we press them relentlessly, like we did in the FA Cup final.
So we could very well win. But probably not, I would also bet on a City win, like you.
What is a certainty, is that over a 38-game season, City will batter us points wise, no matter if we happen to take points off them.
And that is really all that matters in the end when the league medals are handed out.
If we won 36 of our league games, we could lose both our games to City 100-0, and we'd still be the champions.
We should never judge United based on one-off games or cup runs. Anyone can beat anyone in single games, or knock-out games. And United are often hard-working and put in a shift in the cups, or in single big matches in the Prem. The only way to truly judge United, is by their points tally in the league. That's what shows true progress, because you can't fluke or counterattack your way through 38 games and win the league, like you can in a cup or in single games here and there.