In my experience it's very hard to make some money on Medium. First, the writing has to be exceptional and second, you have to get picked by publications. Third, monetization isn't even available in some regions (like in my country - Lithuania which is part of the EU).
On the other hand, here on Steem (and especially since recently Steem Engine has been created) I can get rewarded in multiple tokens I can invest myself to facilitate the growth of my account. It's just there are so many opportunities here on Steem these days. And new ones are popping up every week.
And the best part is that I don't have to be picked. I can pick myself...