Erroll Garner, one of if not the greatest jazz pianist wrote "Misty" as a piano jazz trio melody, and it's fabulous the way he played it. Then someone wrote words to the tune and Johnny Mathis sang it. It became known in the 60's as "Music to Get Laid By".
Both were important.
"The Second Barbra Streisand Album", recorded while she was still a young early 20's, has such raw emotional singing from one of the great voices of all time, that the lyrics are obviously dominant.
Then there was Santo & Johnny's "Sleepwalk". Straight instrumental.
How do you determine which is more important with Clapton or Zeppelin, or Hendrix or Airplane.
Then there's Tchaikovsky, Stravinsky, Mozart, Bach, Strauss, and on and on. Obviously the melody.
I'm not familiar with a lot of the more recent groups mentioned, but I would have to imagine it's the same. It's going to depend more on the individual piece, the intent of the artist, the quality of the recording etc.
As I say in my sig, Just enjoy the music.
BTW, I'm trying to listen with a more open mind and ear to some of the newer stuff, especially after being figuratively handed my a** over some comments. Still don't like it, but looking for the artistry in it. Some does have some obvious, serious artistry. WFCF plays a lot of less known groups as well as more commercially known material. I listen for about 1/2 hour a day, and it doesn't hurt nearly as much as it used to. I'm learning and opening this old hippy mind again.