Whereas Medium works better for network effects/SEO (and why it became super popular before Facebook/Twitter became the most reliable methods of distribution for personal articles), Substack has a better writer/reader relationship, which matters when trying to make a living off of it. Although as a result, it incentivises "thought leadership" more than Medium, which is funny in retrospect since Medium was the blogging platform that started the trend.

Conversely, technical content doesn't do as well on Substack.