More than just considering the reader's interests, it's also against the author's interests to use Medium. They've become more and more draconian, bloated, and, well, the same as any other venture capitalist ultra-growth-oriented company. The chickens will come home to roost, and if your content and your audience is on Medium, moving them elsewhere is going to become increasingly difficult over time. Ability to export your content always trends downwards as the desirability of doing so trends upwards - a business which is struggling is not going to make it easy for customers to leave.
Always write on a domain you own. You don't necessarily have to own the server, but if you own the domain, you have the freedom of choice.