The Pew study I linked earlier actually had Fox News viewers rated slightly higher (one spot) higher than USA Today readers in their ranked array of how well consumers of news from various studies did on questions about current events.By contrast, some media sources have a positive effect on political knowledge. For example, people who report reading a national newspaper like The New York Times or USA Today are 12-points more likely to know that Egyptians have overthrown their government than those who have not looked at any news source.
The Public Mind people adjusted results for demographics such as education and income while Pew did not. However, Pew did report demographics and reported that USA Today readers tend be be more educated and have higher income than Fox News viewers. That means it's very likely that adjusting the Pew Data for demographics would have increased the extent to which Fox News viewers "looked" to have higher knowledge of current events than USA Today readers.
So it can kind of depend on who you ask and maybe also who you survey (like New Jersey vs. the entire US).






