Taking both Barcelona and Manchester United's current performances into account, we can conclude that Barcelona is a better side than Manchester United because they have a couple of wins in their last matches and have recently surpassed Real Madrid to become the top of the Laliga table, whereas Manchester United is still struggling to return to the top four in the Premier League table. Nonetheless, the match will be difficult because we both know that Manchester United has a strong team capable of defeating Barcelona, even if their Premier League performance is not as good as Barcelona's in Laliga.
We can't conclude yet which club is far better because both clubs play in different leagues having their respective weakness. Barcelona were unable to enter the knock out stage of the Champions League , while Manchester finished the same point with Real Sociedad just 1 point GD separated them. It is going to be a home and away game so aggregate will count as well as goals. Ten Hag seems to give in more to the Europa League than he does in the Premier League and United has a more balanced team than Barcelona at the moment all they need to is utilise them.
I believe Erik ten Hag has given his best for Manchester United for the Premier League and also for the Europa League, because the competition in the Premier League is difficult so of course it is not easy for Manchester United to be a strong team in the top four.
I'm sure, if Barcelona played in the Premier League then it looks like Barcelona won't be able to be strong in the top four either, because the Premier League has a more difficult competition compared to other leagues.
Therefore, I personally believe that Erik ten Hag will be able to give good results for Manchester United, because if I look at Xavi's quality so far at Barcelona they are only good in the local league or in La Liga.
But if Xavi gets a tough high-pressure opponent or competition in a European tournament or in this case the Champions League and/or Europa League, Xavi still can't come up with the right strategy for Barcelona.
Although indeed, I admit Barcelona have a more luxurious squad, but that still does not guarantee Barcelona wins because the coach factor at this moment is also very important and for me Erik ten Hag is still better than Xavi.