Zialucia:
The major differences, imo, are the Norte is hilly coastal walking versus mountain, vineyard and farmland on the Frances. There is also more road walking on the Norte than Frances. The Norte is a little tougher day in and day out than the Frances. There are no thousand meter climbs on the Norte, such as the Napoleon route out of SJPdP. That said, there are many 500 meters steep up and downs. The Norte gets a bit easier the longer you walk with the last third being the easiest, imo.
There is plenty of accommodation on each route. That said, you will probably be staying in a hotel or private Albergue more often on the Norte.
Both these routes are well way-marked. The Norte does offer a lot of alternate routes almost daily. The Norte, if you find hard pan walking not to your liking, offers an option to switch to the Primitivo after Villviciosa.
The Norte is less crowded than the Frances but still well populated.
Hope this helps. My experiences have all been in the Spring (March/April) not the Fall.
Ultreya,
Joe