I would say that the purpose of sacred music is to uplift the soul and body and make the listener more in tune with the sacred nature of the liturgy (Mass and other).
As the message of the Gospel is to unite the world in Christ and bring souls to Heaven, I would say that IN GENERAL “art music” is the best choice.
While no music has its advantages, not everyone is meant to be an ascetic.
Bad music should NEVER be one of the choices.
So called “art music”, which I take in this article to mean music sung by a choir or more traditional hymns is the best choice BUT there is now and always has been art music that is not appropriate for liturgical use. The Mass in B Minor and The Coronation Mass both come to mind. The Mass is not a performance and when the liturgy has to “wait” for the music, there seems to be a disconnect between the purpose of sacred music and the execution.
I will say that on major feasts such as Easter, Christmas and Pentecost, having an involved and long Mass setting sung as part of the liturgy is appropriate to emphasize the importance of the feast. However, the congregation and celebrant shouldn’t sit down part way through the Credo or Gloria just because it is longer than usual. That instantly signals that this is a performance instead of prayer.
For some thoughts on the “necessity” of congregational singing, I recommend the book
A New Song for the Lord by some guy named Ratzinger.
