The composition definitely. I'm not a lyrics guy, and I'm firmly in the camp that hold that lyrics are not music. (They're supplementary to music, and the vocalist's vocalizations are musical, but the meaning of the words being said are not inherently musical.)
Well-written, well-performed, well-put-together songs are what I like. I don't give a shit about an artist's look, I can't remember the last (non-Weird Al) music video I watched, and danceability can go to hell for all I care.
(Perhaps my username (zeuhl being one of the odder, more obscure genres of rock) and avatar (Genesis-era Peter Gabriel) betrayed my musical preferences prior to this.:biggrin1