While I consider Arsenal favorite for the Europa League title, Manchester United is not favourite for me at the moment. Manchester United will play their next match against Barcelona. If Manchester United is able to win against Barcelona, then I would say that Manchester United has the right team to win the Europa League title.
I saw Manchester United's performance in the group stage. Neither their performance nor their match strategy was good. If you perform like that, it is impossible to win the title. Their performance will inevitably improve. At the same time, the internal conflicts of the party should also be resolved
Manchester United have quit well current performance in group stage this season and have the same points collected with Arsenal, I don't think what your reason about Manchester United have underperformance this season after win 5 matches and have 1 loss at group stage. I think with play off round match against with Barcelona looks unlucky moment for United because loss difference goals with Real Sociedad although last matchday success beat Sociedad at their home.
Still have possibility for Manchester United with Europe League tittle actually if can beat Barcelona in play off round begin at February 17th for first leg and second Manchester United playing home on 24th February.
Manchester United's performance in the group stage was really good? I don't think so. Although Manchester United won 5 out of 6 matches. But they have to fight hard to win every match. Even against comparatively weaker teams, they cannot dominate the match. If they can't dominate against weak teams, how can Manchester United win against big teams like Barcelona or Arsenal?
However, whether the Manchester United team is worthy of winning the title will be proved in their upcoming matches. Manchester United will undoubtedly become favorites to win the Europa League if they beat Barcelona.