Grand Canyon du Verdon Route des Cretes
     photos by: Francis     
The top picture here shows, in the background, the South road on the other side of the gorge, and you can clearly see the section called Tunnels de Fayet, which is one of the best viewpoints on that route - but you can also see how that road wanders away from the lip of the gorge, which is a major disadvantage of the southern road - it offers the best views, but also the most dreary sections of road.
This Cretes circuit is interesting in offering good views like this down onto both the other roads.

By including this 22km 'Route des Cretes' circuit as part of the Northern route, the length and hilliness of the two routes is more or less equalised - both are just over 50km long, with the north side (including this circuit) offering more frequent and continuous views of the canyon, the south side offering the very best individual viewpoints.
Without this circuit, the north side is very much the easier route, but ultimately not so spectacular as the other two roads.