I say Maiden. Reason being, the first seven Maiden albums are all brilliant, some of the best metal albums ever made. Even though Saxon are producing quality metal albums these days and Maiden are going more progressive, Saxon have yet to produce an album that comes even close to any of the first seven Maiden albums. In saying that though I still need to hear more of their stuff but I'd be very surprised if they had an album as good as Killers or Number Of The Beast or Powerslave or Seventh Son anywhere in their back catalogue.
