Re: Are these 2 readers speaking in RP/BBC English? Which one should I learn from?
Both of the readers speak excellent English, and certainly represent RP. Either one of them would be an excellent choice upon which to model your spoken English.
The only differentiation I would make is that Stephen Fry is reading from a children's book, and is modulating his voice and accent in an animated fashion to represent different people speaking. The other speaker is reading from an academic lecture, so his voice is less animated and maintains a more constant tone throughout; perhaps making an easier model for you to follow.
I'm not a teacher of English, but I have spoken it for (almost) all of my life....