If Marseille win by 1 at home, the match can go to extra time and penalties, if they win by 2 they will advance. I don't think Benfica will pull back themselves too much in defense, it would be a mistake if they do. This is a draw where both sides can advance and it's very difficult to make a choice.
Milan, on the other hand, have to beat Roma away. If Roma can keep the scoring advantage from the first leg at home, they will be the Italians to reach the semi finals. This match is also very difficult to decide. It seems to me that Milan will score the goal. But we'll see if it's enough for them to pass the round.
For Marseille vs Benfica If you look at the performance in their respective leagues, Benfica is far superior, but Benfica will play at Marseille's home ground. Of course Marseille will score a goal early in the match to equalize. If Benfica is not careful, goals will definitely be scored again. Likewise, with Roma vs Milan, I think Milan still has the potential to go to the next round because in the first leg they are not too far away in the first leg. Of course As Roma appeared determined and defended the results in the first leg.