Who is a better rapper? Jay-z or Eminem?

Jay-z and Eminem are both tremendous rappers, an if you think either one sucks then don't post an answer. So obviously eminem has more multisyllabic rhymes, layering lines, and overall wordplay, but Jay-z has topical references, vivid word pictures, and Great song composition. Not always great raps, but great Songs. So who is the better? Please give reasons to your answer. Not just "Ems the **** yo" no pointless answers.