I'm not so sure about that. Magary writes every day (at least), Simmons hasn't written an article in months (maybe years). Magary also has vastly improved as a write (read his first book and compare it to what he writes now), while, when Simmons writes, it's the same bullshit that he's written for the last 20 years.
In other words, when it comes to a writer comparison, Magary owns that lane over Simmons. All day and it's no contest.
I couldn't tell you about their podcasts because I don't listen to either of them, though from what I can glean, Magary seems a little more intellectually curious than Simmons and seems to challenge himself more. You can argue whether the latter is a good thing or not (I do, but I find the thought of listening Simmons bullshit with Uncle Sal over this week's odds to be fucking torture), but I understand the ethos in giving the people what they want and if it ain't broke, don't fix it and other cliches.
If there is any resentment (and there probably is), I think it's that Magary a. doesn't like New England and b. can't stand how Simmons was able to get to where he is simply by being at the right place at the right time. In the first point, whatever, I don't care about that, there's a lot of people burnt out on Boston. But on the second point, I think that Simmons workED hard, but has been coasting for years. I think that is a reasonable (maybe the wrong word) reason not to like someone. Fuck, Simmons made his name on beating up writers (Shaughnessy, "More tapioca Mr. (I can't remember the NY writer he'd say this about, my memory sucks), EEI, the entirety of the Boston and National sports media), who he deemed was lazy, so it's not exactly an unfounded accusation.