It Is superior many time over to Madeira Black,when we compare production,adaptability to difficult climate ,cold resistance, health,etc,---But:
It is not as tasty or as flavorful,as Madeira Black ,when Madeira Black get ripe properly,in the proper climate,in full sun all day.
In the above conditions,for Both cultivars,taste and flavor only,:
Marseilles black vs,can be an 8 or a 9,out of 10.
Madeira Black is a 10,out of 10.
Of course for us in cold climates with short Summer season,Madeira Black grow to slow,die to fast from cold,produces fruits to late,and only in rare occasional years fruits ripe to perfection,so for us ,Marseilles black vs is a better choice,that will ripe every year, and that is why people like it so much.