Passage A Music does not always gain by association with words.
Passage A
Music doesn't necessarily get better by having words associated, but words can be improved by having music associated with them, since music is better able to express the deepest emotions.
In general, combining words and music is mixing two effects and diluting the purity and emotional power of each separate art form.
However, you can still do good stuff by combining them, as long as the words serve the music, which is the more expressive half. That's what's happening with opera. The words of the libretto aren't the main source of aesthetic value; the emotional range conveyed by the music is.
Passage B
There are two types of operas: music-dominant and music-balanced (music is the most important factor, but it's roughly balanced by other factors). The potential third type, music-subordinate, hasn't really ever taken hold.
No matter the type, when you're aesthetically evaluating opera, you shouldn't look at music or poetry in isolation. You judge the music by whether it serves the words and the words by whether it serves the music.
Opera's essence is that the effectiveness of the music and words are deeply intertwined.
Overlap / Disconnect
Both passages were discussing the relative impacts of words and music, including whether words are better w/o music and vice versa. Passage B cared way more about opera, whereas Passage A only barely addressed that topic.
They do seem to have a disconnect when it comes to opera. Passage A said that the aesthetic value does not depend on the words; it depends on the emotional range of the music.
Passage B thought the aesthetic value was more about how the words and the music function to enhance the other.