this trip for me was so long ago, I dont recall the details, but what stays with me (a really enjoyable trip btw) is that it was harder with the climbs than the Pyrenees, just a general impression but I trust my gut on this one.
Seems to me that the little ups and downs wherever a river came to the coast were the worst, and tiring. You'd be up from sea level a given amount, then at a river you'd zoom down a steep hill then schlep up a steep climb. Repeat.