The spokesman engine Google, wanted (he says that) "break a myth" in his latest video sent to SEO and webmasters. Someone asked, "What is about the percentage of Page Rank that is lost during a 301?" The answer to Matt Cutts is a bit convoluted: "the amount of PageRank that is dissipated through a 301 is exactly the same as that dissipates through a link."
Matt Cutts recalls that, in accordance with the original scientific articles on the Page Rank, the more links a page has, the more Page Rank transmitted is diluted. But the total Page Rank is passed down "from 10 to 15%." This is the same part that would be lost, according to Matt Cutts, in the case of a redirection type 301.
The "myth" that a redirection lose less Page Rank that a link is supposed to be shattered with this video. Matt Cutts also said that Google does not see why, today, these principles change.