It's quite reasonable that Real Sociedad is more favored than Manchester United because Real Sociedad will have the advantage of playing at home, and as we know, Man United has inconsistent performance. But still, that doesn't rule out the fact that Man United could still make a surprise, because even though they are in ruins in the league, but what is happening in the Europa League is the opposite, where Man United can perform well and they get to the last 16 without having to go through the play-offs.
I see Manchester United's form as an anomaly. They have been very poor in the EPL but so far they have been one of the better teams in the UEL. United finished third in the standings and they are still unbeaten. Real Sociedad are the favourites in this match and in fact Sociedad have been better than United in the last few matches. But as you said United could spring a surprise in the match. But even so I still pick and support Sociedad to get the three points. They are playing at home so that will give them the motivation to win the match.
I can agree with you that real sociedad is in better form than Manchester united but I cannot agree with you that this means that Real sociedad is going to win Manchester United tonight.
Manchester United indeed has been having a bad season. In fact not only this season but from the past seasons but there is something remarkable about Manchester United this season and that is they have a flawless record in the Europa League of this season. I think they have been going on beating and they have a good chance of winning the Europa League. Since this is the only tangible achievement that Amorim could get this season, he will me more serious with it.