I agree with you football wise, but psychology wise, Arsenal is in great advantage over PSG. Arsenal being able to defeat Real Madrid home and away has automatically given them an edge over PSG. PSG is coming to the match psychologically defeated. If Arsenal build on this, they will coward PSG and win them.
Real Madrid has eliminated PSG 3 times under 4 season that I can remember and if Arsenal is strong enough to finish this guys in the quarter final, PSG shouldn't be a problem, they just need to find their weak points the way they did with Real Madrid, the same strategy they used to unleash many goals in the first leg, the other leg will be stress free.
However, the way Arsenal scored goals, they don't do much damages like other teams, it's only in this Quarter final they have had much number of goals, if they don't do that in this semi final, they will suffer this loss to PSG and wouldn't be able to advance from this stage.