I myself would say lyrics are slightly more important. The music can be very catchy or whatever, but when the lyrics simply suck, I don''t like the song too much

And it could be quite important to know what they are singing, as then you could avoid some misconceptions. For example when people say a certain song is romantic, because of the tune and a part of the lyrics, but when you read the complete lyrics, you notice that it is about divorce or so. So in those cases, to avoid misconceptions, the lyrics are important
Though a nice melody is appreciated sometime, especially the right combo of good lyrics and nice music.