People act differently towards different people. Ron has been chastising the right for so long and so harshly. The people on the right know that Ron is correct but people will have a hard time admitting that to Ron or agreeing with Ron because as human beings it's somehow harder to admit or agree when one has been harsh with you or critical of you..
So here comes Rand. Saying all the same things as dad in a smoother way without the criticizing.. and since he comes with no prior history of attacking anybody it is much easier to get people to agree with him.
Its why back in the day Hannity would be more angry with a Ron Paul who would attack him from the political right than with say a lefty hippie socialist who would attack him from the political left.
That is part of it, I agree. But Ron's purity also galvanizes people. He really DID start the tea parties, and launched numerous political careers and new activists across the nation.
If neither Ron nor Rand will win the presidency this time around, Ron, imho will have the larger impact on the future dialog, will inspire waves of more people and will make the future more receptive to the liberty message. However, once he does that, Rand is the one who is likely to someday be president. But I think, in the end, he needs more support than there exists now (given the other flavors of tea party candidates running), and Ron, and his ripple effect, can galvanize that.
Playing it safe convinces people at the margin, but doesn't inspire others to their own individual action in the same way, and to me, that is the main difference between Ron and Rand. I like them both, and I would vote for either. But Ron inspires me.
However, Ron is getting older, and may not want to run. If he decides not to, as soon as he says that, fewer people will go to listen to him at events, and he will have less opportunity to galvanize people and get them on board. Perhaps that is part of why he doesn't mind taking his time to announce, one way or the other.