Take a second look at the mosaic. I’m constantly amazed at how the artists of the ancient world were able to portray so much realistic human expression to the face.
European artists after the Dark Ages took awhile to develop those skills while later Byzantine art went in the direction of represational iconic art.
Those guys were really good.
One advantage of using the mosaic method was that the artist could fiddle with the pieces until he (or she I suppose) got the desired effect. Also, mosaics were custom made for the available space. :’)