The other half is an intangible quality that we might call personality or attitude. It is the why. These aren't each 50%; it's more as though each were 100%. Take Emily Dickinson. You can say that she is strong in logopoeia, or the quirky relationship to the words themselves. That she does interesting things with the meters she chooses, and introduces weird pauses and other prosodic devices, or that her poems appeal to the five senses. All that would be true, but without that peculiar attitude, all that would not necessarily add up too much. With Baudelaire it's the same thing. It's not just the cold mastery of French verse, but the attitude that makes him Baudelaire. It's what O'Hara meant when he said "you just go on your nerve."
The attitude won't be the same for every writer; in fact, it will be radically different, and will be the most original part of each writer. That is why poets who don't seem as good at charging language in the Poundian sense can still be very interesting. Levertov is a better imagist than Creeley, but I feel more drawn to Creeley's attitude than to hers. Eileen Myles is strong in attitude, so I don't care if every poem is strong in other ways. Many of her are, though.