Everyone likes and will always like Ron more; that being said, Rand is 100% right on the Iran sanctions, and his views are much more mainstream compared to his father. Paul's base, while still not large enough to win, has expanded massively. Rand is a strong contender for the nomination.
Serious?
Hannity and the other conservative talking heads don't go into a seizure when they mention Rand's name, since he is quite good at talking and acting like a standard southern/midwestern social conservative when it counts and keeps the libertarian tendencies to a minimum in comparison.
For that reason, I much prefer Ron to Rand, especially since I don't really see Rand taking as many principled stands (from what I've heard he's about as likely to lose Kentucky next election as Nancy Pelosi to lose San Francisco, but he still can't do as much as a senator) and he just doesn't rub me the right way sometimes. Mind, I don't really like having libertarianism in the US being basically represented by a lone 73 year old congressman with a pendant for making poor short term political decisions.