In-context editing in concrete5
The concrete5 admin is one of its claims to distinction compared to Drupal and other older CMS systems. It features edit-in-place technology that makes editing pages more intuitive. Site managers can simply navigate to the page they want to edit, and click on the content they wish to change. Why hasn't edit-in-place already taken over the CMS market? Probably because most fledgling attempts at it have failed to achieve sufficient usability. But concrete5 seems to have found a way to implement edit-in-place successfully, so that is a big step forward for CMS systems.
Traditional page editing in Drupal
In contrast to concrete5, the Drupal admin takes a more traditional approach. You access it at /admin, login and are presented with all the admin options. In Drupal 7 there are some aspects of edit-in-place, in that there are links to the admin from certain page content areas. But this support is spotty, and generally speaking, to edit something in Drupal means going to the appropriate place in the admin section.
Generally the concrete5 admin is sleeker and more streamlined that the Drupal Admin. However that sleekness may come at some functionality cost, because as a relative newcomer I find myself wondering "where to go" to do various things that in Drupal are common and can be found under well established menus such as "site configuration". In some cases that might just be my own learning curve with a new interface, but I think overall concrete5 has far fewer options for site configuration "out of the box". Which might be a good thing, considering most newcomers to Drupal find themselves overwhelmed by the horde of Drupal admin options.