Nobody is thrashing Arsenal. We might not get through but it will be at least competitive. Our defence will make sure.
I'd rather play Real than Atletico though from the perspective of getting through. Real are obviously a very talented side but they like to attack and for all their A player attackers they aren't super strong in midfield and at the back and I think we could overpower their midfield, with our defence doing a decent job of keeping Mbappe/Vini at bay.
Atletico on the other hand are Arsenal's worst nightmare. Defensively solid, able to play a low block, effective on the break. No thank you - bring on Real.