The CNN analysis of the performance of Palin and Biden in the recent debate simply means that Biden is the better communicator, that he reached a wider audience. In reaching an audience at the eight grade level, he has automatically reached all those above that level. He had, on average. more sentences per paragraph which implies they were shorter sentences and therefore more likely to be clearer and comprehensible.
Theoretically therefore, more members of the American electorate picked up and understood Biden's arguments. That is what politicians should always strive to do - reach the widest possible spectrum of the electorate. Joe Biden was the better tactician in the war of words.