I have done both Haven and YC.
Several NCL Haven and suites, from non Haven ships, Sun with aft 2 room suite and huge balcony (same suite twice), which was my favorite until the Epic DOS which was incredible and my first forward facing. I love NCL Haven.
I chose MSC with the match and because I cruised solo the YC interior spoke to me. I did not spend a lot of time in the suite but rather in the YC and the spa.
While in a Haven suite I definately took advantage of the suite and balcony. I expect I would do the same on MSC if I cruised with someone else and in that case, chose a larger suite with a balcony.
I never felt the MSC inside diminshed my YC experience. I loved the pool area and al fresco dining. But I also loved the EPiC Haven pool area with the POSH right there.
I give NCL Haven restaurant the edge, by a good margin. But the specialty restaurants tie.
Where NCL has an edge, and this is a matter of preference… not everybody cares, are the Haven staff and ship officers who are friendly and accessible. I cannot remember anyone from MSC, but NCL, lasting memories.
Both great. It is NCL HAVEN with an edge if money is not an issue. However, the experience MSC YC offers is a very good choce if it is. I feel blessed to have done them both.