Medium has far better quality in articles, but with Steemit you could potentially earn quite a lot more than on Medium.
I swear I've seen a similar question in the Serious Discussion board or something. There was one really good reply.
I've been active on Steemit for about 3 - 4 months now, I quite like it.
You do need to build a network of friends there that will upvote your posts. Usually you'll find curation groups on Discord, perfect place to start building those connections.
Steemit can be really good for publishing crypto-related content.
I think it might have been this reply, not sure though:
https://bitcointalk.org/index.php?topic=3114382.msg32317082#msg32317082Why not publish all of your articles into both ?^^
That's something you could do, but can cause some problems on Steemit. You might get tagged by some of the anti-plagerism bots.