It doesn't necessarily need to be an either/or scenario. I have a hand-made blog built with Jekyll, but I also cross-post lots of my articles to Medium.
Honestly, I'm not the biggest fan of Medium, but it's undeniable that you can use it tap into a large audience if you do things right.
I'm a big believer of "building your own platform", but still trying to reach people where they are. Lots of people read on Medium, so post on Medium! But don't be shy to throw in a link to your more centralized spot on the web as well.