PSG eliminated Liverpool and it's quite hard to say Arsenal is playing better than Liverpool,
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...
I didn't say humiliated, I said eliminated, and it doesn't matter how they did, it's just that they managed to do it, and if they beat Arsenal again in overtime it would be the result that would count, not what the difference between gameplay. And as I speak, bookies tend to agree with me, PSG is still the favorite for the qualifying but not the favorite to win the game on Arsenal's home turf, much like Real was favorite in the second round for the win but not for going to the next stage.
Here I agree with you that PSG should not be favourites in London... Arsenal have shown that they can beat any club in the Champions League and PSG in my opinion are no stronger than Madrid at the moment... I compared PSG's game when they played Aston Villa away and it seems to me that Arsenal will play even better than Villa... But I still find it hard to make a prediction who will win... Both teams play well in attack and I expect BTTS and a lot of corners in this game...