Diana Krall has become very, very successful by performing in the songbook tradition. Much like Tony Bennett, she has mined the modern popular song genre, and her albums are full of "classics". (I joked to my wife that she was aptly named, since she prefers very s-l-o-w tempos!)
Cassandra Wilson seems to have taken a page from the Diana Krall instruction manual lately, because her album "Loverly" features songs like "Gone With the Wind", "Caravan" and "The Very Thought of You". As much as I love the album, I enjoy her older titles even more, especially "Blue Light Till Dawn" and "New Moon Daughter". On those albums, her arrangements are a bit more interesting, as she performs her own take on such songs as "Tupelo Honey", "I'm So Lonesome I Could Cry", and even "Last Train to Clarksville" (!)
Two different styles, but both excellent performers.