If you want to descent totaly safe on a long descent, you'll definitely need rim brakes!There is no way in hell I will ever ride a road bike with discs, I experienced brake fade while riding one of my disc MTBs on the road and for those who have never experienced it, it is truly terrifying. I had no brake power at all and was flying down a hill going 45mph, only way I was able to stop was by putting my feet on the ground to slow myself a bit and eventually hopping over a curb to crash into some bushes (neither of which I could have done on a road bike with cleats on). Sure, if you know how to ride them you won't likely experience brake fade, but whos telling buyers not to pad their brakes during long descents? I knew about the issue before it happened to me anyways, even experienced riders who know can have careless moments.
Like this: https://www.youtube.com/watch?v=haEbtHiUcBc