I failed to do a literature search before I posted previously on Glenn Greenwald's complaints about nepotism and the Senate. Turns out that I didn't make a mistake, because the key paper here is unpublished work by Tom Schaller and Geoffrey Vaughan that Schaller talks about over at FiveThirtyEight. Turns out that in fact family ties in the Senate have steadily decreased over the history of the Republic.
Schaller doesn't offer any thoughts on media nepotism (the lasted flare-up was sparked by Bush's kid getting hired by NBC, but since the bulk of the "media" used to be newspapers, and most of those were family-owned, I have to believe that nepotism is less of a big deal than it was, say, a hundred years ago.
So my original claim of "no difference" may have been far too generous to Greenwald. Looks like the answer is: the opposite of what he thought.