Probably feeling, for me. I tend to like music that's equally slow and intense. Tight musicianship is, of course, always appreciated, but I listen to music mainly for the feeling it gives me and the mood and atmosphere it can convey. Many of my favorite albums were early releases from my favorite bands, and while they're not nearly as polished as their later works, I enjoy the rawness and imperfection of it, because it sounds natural and somehow more passionate to my ears, even though some people might call it boring or amateurish or immature. I love when songs have lots of different riffs and are doing something different or interesting technically, but if it sounds wrapped in plastic and vacuum-sealed, I'm probably not going to like it.