Hey Bob - I haven't walked the Portuguese route, so can't add much value there, however, I have walked a few of the other popular routes all of which I recommend for various reasons...
You have walked the CF, so you have already experienced the most "developed" Camino of those I've walked. I say developed because this camino seems to have the most convenient stopping points, the most infrastructure, support for both hoteligrinos and albergrinos, many lavadoras y secadoras, vending machines on the side of the path, etc. The best part of the CF for me has been that this is the one where you'll always meet a bunch of like minded people, eager to explore, experience the "Camino Magic", many for the first time. Don't get me wrong, its fields of wildflowers, mountain vistas, everyday rural villages, and glorious historic cities make the CF a stunning visual experience. But when I choose to go back and do the CF (as I did again last year), it is because I know it is my best opportunity to form lasting relationships with interesting international souls and share some life changing interpersonal interactions.
One thing, being from the beach myself, that I missed on my first Camino experience was the sea. Only on a second trip along the CF, walking with my sister, did I realize Spain's coast offers a wonderfully Spanish interpretation of our common Mediterranean climate's coasts.
The walk on the Norte from Irun to Santiago is sometimes so fantastically beautiful that I found myself laughing out loud while eating a bocadillo on the side of a cliff overlooking the surf, or feeling jealous of horses enjoying lush grass fields with a beach view. If you like the sea, especially the first half of the Norte is awesome. The first few days are rather alpine, but then again you find the sea. Note, however, that because you're near the coast, the timing of this camino can be pushed slightly to the warmer times of year to avoid rain and naturally cooler temperatures. Also, when I went, the traditional Camino infrastructure was stressed somewhat, arriving in multiple locations with Albergues filled. Luckily, however, there seemed to always be a place to stay, where credit cards come in handy. There are fewer people generally, but still some lovely examples of "Camino Magic" such as at Guemes. This camino, for me, was about the coastal views.
The Primitivo - starting in Oviedo (some cross over from the Norte before, and some travel the San Salvador from Leon [as I did]), enjoys a good deal of vertical gain and loss among a forested interior. Its been a while for me, but I remember a constant up and down, and a more modest camino infrastructure. I never had trouble staying where I wanted to say, less so because of the availability of facilities, but rather because of fewer other perigrinos. I did have a magical dinner along the way with 14 other perigrinos of various nationalities, but for me, this camino was more about physical endurance and accomplishment in an alpine environment.
Sorry for being so verbose. I enjoy writing about the different paths as I can remember again each experience as if it was yesterday.
Someday I too will do the Portuguese. My next year's trip will be on the VdlP, which, this planning season has revealed to be a logistal challenge, though certainly doable with all the help offered here on this forum.
Buen camino,
Damien