If something you write is a big success, especially tech/programming related stuff, chances are, most of the traffic over time will come in from search engines.

If something you write is a big success, especially tech/programming related stuff, chances are, most of the traffic over time will come in from search engines. Also most of the SEO juice (backlinks etc) comes in shortly after publishing. If Medium/other-platform goes defunct or decides to remove you it will be very hard to rebuild it. Much better to separate distribution from hosting. The small boost they will give you at the beginning is not worth it IMO.