Manchester United vs Fc Barcelona match has been discussed much more than every other Europa league match. Maybe that is because the two clubs are anticipated by many, to be the champions of the Europa league title. But let me put it to u that neither Manchester United nor FC Barcelona may end up pushing through the final stage of this competition. Let us not forget that the likes of Juventus, Arsenal, Ajax, union Berlin and PSV are salso hunting vigorously for this same title. Most of these clubs with little or no up of being champions in their lower league.The table is not revolving around Man united and Barcelona only.
This season the Europa League is difficult to predict because there are many great teams in it. Some of the teams you mentioned are teams that are not weak in their respective local leagues, so there are many possibilities that could happen in the Europa League this season even though the ones that are most often discussed are Manchester United and Fc Barcelona. But they both could have been knocked out by some of the teams you name in the Europa League this season.
Difficult or not , I think Arsenal has the first chance to win Europa League because if we take a closer look, they finished Group A with 5 wins out of 6 games and have a +5 goal difference so that tell us clearly that they like to score a lot and once they score , they won't lose the game. Now , in 2nd place , I might give it to Betis Sevilla and not Man.United. Why ? Well , United are really looking like a complete team ? I say no. Betis on the other hand , have played with almost same players for 3 years now or even and this makes them a strong team and very united with each other to complete their goal to win an European Competition.