Something I’ve been thinking about, too, with Advent here.
From what I gather, and from various Catholic sources, I’d agree that there’s no right or wrong answer, especially since we’re not obligated to pray the Rosary under penalty of sin in any event.
My Rosary brochure says that it’s “optional” to pray the Joyful Mysteries on Sundays during Advent and the Sorrowful Mysteries on Sundays during Lent.
From two Catholic sources:
After the discussion of assignment of the Mysteries to certain days of the week:
**Where this system is rigidly adhere to, conflict can arise between the content of the mysteries and that of the Liturgy of the day: the recitation of the sorrowful mysteries on Christmas day, should it fall on a Friday. In cases such as this it can be reckoned that “the liturgical character of a given day takes precedence over the usual assignment of a mystery of the Rosary to a given day; the Rosary is such that, on particular days, it can appropriately substitute meditation on a mystery so as to harmonize this pious practice with the liturgical season”(242). **Hence, the faithful act correctly when, for example, they contemplate the arrival of the three Kings on the Solemnity of the Epiphany, rather than the finding of Jesus in the Temple. Clearly, such substitutions can only take place after much careful thought, adherence to Sacred Scripture and liturgical propriety.
From 2002, noting the insertion of the Luminous Mysteries and the newer assignment of Mysteries to days, which assigns the Glorious Mysteries to Wednesdays and Sundays:
This indication is not intended to limit a rightful freedom in personal and community prayer, where account needs to be taken of spiritual and pastoral needs **and of the occurrence of particular liturgical celebrations which might call for suitable adaptations. **What is really important is that the Rosary should always be seen and experienced as a path of contemplation. In the Rosary, in a way similar to what takes place in the Liturgy, the Christian week, centred on Sunday, the day of Resurrection, becomes a journey through the mysteries of the life of Christ, and he is revealed in the lives of his disciples as the Lord of time and of history.
What I plan to do this Advent is keep to the traditional schedule (including the Glorious Mysteries on Sundays). This schedule makes sense to me because it has an even split between the Joyful, Sorrowful, and Glorious Mysteries (twice per week each). But if time allows I’ll insert an additional five decades on Sundays with the Joyful Mysteries, in keeping with their relevance to the season.