If you are starting early in the year will you maybe have snow on the early stages of the Francés? Also you have already walked that Camino.
On the Norte, being near the coast, the weather may be better and you do not have to go through the mountains until later. You can follow the Norte the whole way or go through Oviedo and either continue the Norte or go onto the Primitivo. The latter would depend on the threat of snow as there are high passes beyond Tineo, but you do not have to make a final decision until after Bodenaya as you can turn up to the Norte again at El Espin.
Buen Camino