Paris Saint Germain is more favored, because many people think Borussia Dortmund is the weakest team currently in the semifinals. However, Paris Saint Germain cannot take Borussia Dortmund for granted, because when they beat Atletico Madrid it proved that they are also capable of competing and providing something interesting.
Borussia Dortmund will play as hosts first, and that actually benefits them in my opinion, because they can take advantage of that to win the match and that will make them more confident. But don't think that by winning the first leg they can be guaranteed that they will qualify, because we know Paris Saint Gmain also lost the first leg and in the second leg they can win, even if they did it at the opponent's headquarters.
I would not dare to say that Dortmund is the weakest team left, because at least a weak team could not beat Atlеtico like that.
And in fact, in the first match with Barcelona we saw that PSG is not so strong now, and they can be beaten even at home, and in the second match Barcelona simply had force majeure that affected the game, although perhaps they should have simply concentrated more on defense. I would probably also give preference to PSG in this pair, but there is definitely no clear advantage here, Dortmund has every chance of reaching the final.