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.
I also have an opinion that Arsenal will win the European league this season and that is not without reason considering their hard work so as to form strong character for Arsenal's players to date. The role of coach Mikel arteta is also very important to make all the players compact and solid in every match. Even in their regular league, Arsenal managed to break the consistency of Man City and maybe it was destiny for Arsenal to win the title.