The Norte is longer from Irun to Santiago by about 200km than Lisbon to SDC. They both have a lot of asphalt walking but also some incredibly beautiful sections off road, the Norte has a lot more albergues on average for the respective distances. It rains a lot on the Northern coast, if you are not keen on this the times of year when it is less affected are usually around the middle summer months. The Norte and Primitivo have some really special Albergues along the length of them, however the Portugues has maybe the best Albergue of most caminos 12km before Ponte de Lima- Casa Fernanda. Both have variations, the Portugues has the Braga option after Porto and also the coastal route after Porto, the Norte has lots too many too mention, but after Villavicioasa(around 350km from Santiago), the major option is sticking with the Norte or going on to the Primitivo.
I really like the Norte, probably because it was my first camino, however having walked on the CP once,just recently had to change plans to go on a section in the interior of it because of bad news, this is put back to next year. I like both but i feel the the portugues from Lisbon at the moment is very challenging for the first few days, there are plans to change this by the relevant associations.
Mike