Arsenal must also focus on the EPL, they also don't want to lose the opportunities that are right in front of their eyes.
This is why i don't think Arsenal will win the Europa league, they are leading in the Premier league and it is the trophy that they want to win, if they can win the both of them, Arsenal fans would be very happy, but if any Arsenal fan, coach or player is asked which trophy they want to win, we know they will all say it is the premier league. So even if Arsenal beat Sporting and qualifies for the quarter final of the Europa league, Arteta may start rotating his team in that tournament, he would not want his players to be tired for their premier league games. If there is a premier league that can win the Europa league i would say it is United.
The winning of domestic league is always preferable for the clubs just because of this we have many clubs never take UEFA Europa Cup seriously but in this season we have two English clubs both at the top of Premier League are also fighting hard for this cup as well because they are already secured their spots into Premier League and this could be bonus for them specially for Manchester United which is surely looking for having back their golden era back after long wait with Ten Hag is also motivational as he is having good relationship with his players, and they are also responding positively.
Arsenal which is surprise package for this season also having good time under coach Arteta having impressive performance from the first day of Premier League new season and their performance in UEFA Europa Cup is also good, so both are trying their best for having double in this season now who is going to complete this it's all no clear because it's soccer and this is unpredictable game.