grizz,
This subject has been discussed on the Message Board under the title "Rim to Rim or Rim to River to Rim." The initial post was on Oct 10, 2014 and the most recent post on June 4, 2021. To retrieve the discussion in its entirety (lengthy), go to the Search Function on the Message Board and enter "Rim to Rim." You must be logged in to find use the Search Function.
If you do the Rim to Rim this Fall, update us on your take on the comparison of the two day hikes.
Jim