Medium provides you great potential.
Potential to reach huge readership base. If any of your post is picked up and shared by Medium’s algorithm that means your story would reach to many without you having a network. The downside — it would help you if you join a publication. They are preferred over lone wolves. It can hurt you for sometime, unless you write something that catches the eye of publishers or Medium.
But the fact that there is no forced networking — It’s what I would chose.
Wordpress on the other hand is about networking — you open an account, choose your own blog template, and bring a personalized feel to your blog. Plus, if you are naturally good at networking, you would enjoy the crowd there. They are quite supporting. But you have to sustain that by visiting their blog and maintaining the back and forth communication. It wore me out after sometime — as it has many other writers I liked there.
You can start with both — both are easily setup and then see where your heart takes you.