If Arsenal lose to PSG in the second leg it will be disastrous as they will record another season without a trophy in a row. The one goal difference isn’t much, Arsenal have a good chance in the second leg to make history but seeing how poor they have been performing lately in the Premier League I fear they might concede more goals against PSG in the second leg.
PSG did it against Liverpool; they lost the first leg at home 1-0, and they went to Anfield and defeated Liverpool to qualify to the quarterfinal then; this is the same scenario against Arsenal. PSG won the first leg 1-0 at the Emirates Stadium. They had the opportunity to score more goals in the match because they had enough chances, but they couldn’t convert them, which is why the match ended 1-0. They played really well and capitalized on Arsenal's weak points.
Now Arsenal will be well prepared against PSG; they will play with their number six, Thomas Partey, and will also play with the hope of defeating a team they have defeated in the group stage. I don’t think it will be easy for PSG at home; they will experience the same pressure they put on Arsenal in the first leg because they already have a trophy this season while Arsenal doesn’t have any. If Arsenal wins the Champions League this season, it will be the best thing for the club.
This senerio you are bring is quite the same because Liverpool won the first leg at Parc des Princes well at the second leg PSG won against Liverpool at Anfield. So with the look of things if I'm to choose this matter now I will say based on your description I think Arsenal will be the favorite in this manner. Liverpool and PSG really had a hard time during that match but it all went to a different Direction because Liverpool are in a better position to qualify based on a certain reasons, firstly, they have their best performance this season which at the beginning they were all thinking that Liverpool we will win Champions League this season and secondly, they won the first leg at Parc des Princes home of PSG which everyone thought that second leg will be in favour of Liverpool since they played at Anfield but unfortunately, it doesn't went as expected and that was how Liverpool eliminated.