As of now, out of 30 posts each, they differed in only 7 articles (77% similarity):

Classic has:

  Simplicity vs. Choice
  Introducing the BankSimple Engineering Team
  First Clojure conference
  FB vs Foursquare
  Don’t let jQuery’s $(document).ready() ..
  Did Germany experience industrial boom in 19th ..
  C++ Compilation Speed

New has:

  A smartphone retrospective
  Do you understand HTTP Caching?
  Google Suggests changing your name ..
  JITB
  Notes on Writing Good Commit Messages (
  Product to Platform - My Start-up's Summer Journey
  What different sorting algorithms sound like

This is a good benchmark, but not perfect, since people can only upvote what they already see.

Try bringing some schizophrenia to the site: show the "classic" version to the "classic" crowd by default for some time and see if the two versions will diverge more.

Subjectively I feel programming articles are getting rarer on HN.