PSG vs Arsenal would surely be a tough one to predict. PSG barely won over Aston Villa and Arsenal surely is playing better than Aston Villa.
PSG eliminated Liverpool and it's quite hard to say Arsenal is playing better than Liverpool, especially the day one was crowned champions!
If you go by the direct match, Arsenal would be indeed the favorite but from the form, no PSG is still ahead of them at 3.2 compared to 3.5 to win the trophy.
The case for Arsenal at this time, besides benefiting from playing at home, they also greatly benefited from seeing PSG's current focus, especially in domestic competitions they are not in good condition so that indeed this could be a whip of more enthusiasm for Arsenal,
And Arsenal draws with Crystal Palace and Brentford are anything to brag about?
PSG has won the Ligue since April 5th, there is no point in them even playing with the first team in the remaining matches, it makes no sense to stretch your team over something you have no benefit from.
I wouldn't say PSG humiliated Liverpool... They played with a minimal win in England and lost with the same score 0-1 at home... But they were lucky and managed to win in the penalty shootout, so it was not an easy win for PSG... Also they recently played against Aston Villa, where they lost in England, but won easily at home... PSG's last game was against Nice and it was the first loss for them in Ligue 1 this season... Despite the fact that they are already champions in Ligue, they could have finished the season without defeat... I'm sure Arsenal will be a very difficult opponent for them...