I try to view it as a whole package, where they both have to complement each other. If I lean more one way, it's definitely the music, though that by no means means I don't appreciate OPs with baller animation and otherwise subpar music.

I've also found that I prefer the "slower" anisongs (I don't know how to better describe it, but not quite "super hype" anisongs, nor really slow ones. Somewhere in the middle). Build-up is generally important for me, and I find that the chorus is often the weakest part of the OP/ED for me lol