If you're looking for popularity, consider also the premium member phenomenon. Those numbers will never be comparable because they aren't based on ratings and people will misreport those numbers if they're forced to. It doesn't matter to advertisers how many Rush 24/7 members there are, but it matters vis-a-vis popularity.
BTW, Talkers mag (you can google) was started by a guy named Michael Harrison. The archived articles on the website are interesting. Two articles by Ellen Ratner, an interview with Alan Colmes, two interviews of Art Bell. It's now owned by Focus Communications from Connecticut. The CEO is Carole Marks. I have no idea who these people are, maybe somebody else does. I have no doubt that they are underestimating Limbaugh's audience, though.
Brinker is an amazing radio talent. He has been host of MoneyTalk continuously since 1986. He has been on the air almost as long as Limbaugh. Limbaugh and Brinker have different audiences and work different sides of the street. But my vote is that evaluating them as radio talents Brinker is as good as Limbaugh.