[lacker]

Marginal Revolution is a lot more mainstream than Gwern or Slate Star Codex. Tyler Cowen is one of the most influential economists today. His Bloomberg column might have more reach than the MR blog though. So the topics are really different - MR will discuss many issues that are central to the current “national conversation”, with more of a broad-based style of reasoning, whereas Gwern and SSC will go much more into detail on a small set of topics, with more of a “rationalist” style of reasoning. I wouldn’t say they are “seen to be similar”.

Personally, I rate MR quite highly. I just think the reasoning is better-argued and the topics are more often something I’m interested in, compared to basically any other blog. Gwern and SSC are great too though.