Although Miliband has strong intellectual credentials, he is interested in organisation as well as ideas and he would probably seek to revive Labour campaigning at the grassroots. At Westminster he is seen as non-factional figure and he would lead in a collegiate manner. As one of the best communicators in the party, he would also become a magnet for media attention.
I'm always interested, Piaget-wise, in what people were doing from 0- 7. Eddie seems OK from that POV. The usual family-forged personality dynamic is that first-borns become the diplomats and second-borns the rebels. (Third-borns are the comedians). You can't be me, I'm taken