It is a lot of work to run both! But if you have an idea, especially for Substack, it may be worth claiming a cool vanity url/link, since many are still available (whereas many Medium publication names are taken).

For example, I’ve wanted to do a personal finance publication on Medium for a while, and I have with Escaping The 9 to 5, but it was also cool to get the name “Personal Finance” on Substack.