Marseille have done a good work so far. Especially after changing their manager they have been on the rise. We are witnessing its reflections in the Europa League as well. Their performance against Villarreal was really impressive especially in the home game. The Benfica matchup might be a little more difficult but I'm still favouring Marseille to advance. 
It seems that currently Marseille wants to focus more on being in the Europa League because they realize it is not too profitable for them so even though Ligue 1 is still maintained in terms of competence but still the Europa League seems like they want to be better in terms of performance and achievement. In the previous play offs and round of 16 Marseille was always able to maximize their performance well and even they were always productive when playing home which made the situation more optimistic for them in the end.
This quarter final they will face Benfica. I think this match will be very interesting in the end, it's just that looking at the current situation of Marseille and Benfica where consistency is sometimes a problem I think it's still possible for both of them to be in the semi-finals but indeed home games will definitely have an effect if you look at their current match record so that when playing home as much as possible they can take good advantage of it.