Ann Sexton or Sylvia Plath?

They both ocassionally impress the crap out of me, and at other times seem almost careless.  Both have an incredible wit, though Plath's is much more understated and I don't think she gets credit for the dark humor  in some of her pieces.  Frankly, I've been reading poems by both lately (in the anthology Eight American Poets, as well as in Plath's Ariel and Sexton's Transformations) but I'd be hard pressed to pick a favorite, I like them both.  I do think Plath tends to get dismissed more frequently than she deserves.