I see it like Arsenal are still the biggest candidate for the Europa League title. But their toughest opponent seems to be Manchester United for it.
Because after seeing Manchester United's performance against Barcelona as well it is clearer to me. Manchester United don't only care about the English Premier League now. Erik ten Hag wants success in the Europa League as well. I think Arsenal and them can really reach the final both unless they get a matchup before than that. It would be a great joy to watch such a big finale here.
While Arsenal are starting to rise, now they have to compete with Manchester United who are starting to rise as well and could even become their opponents in the European league round later. Indeed, this is something that can be clearly seen and which of the two teams will be able to win the European league title this season. Both Arsenal and Manchester united have had good performances so far in all competitions and as you said, this proves that these two are the strongest candidates so far until the final round.