Multi-value relationship in that case has no a good performance because each value implies a new line on its field index. It means longer write times. Also it has a limit of entries. It's useful when you have a few values to store.
There is another type of relationship: entity group.
The criteria to choose between each method also depends on the type of queries you do and the frequency of updating entities.
In base of the information you provide, I recommend many-to-one relationship.