I've recently migrated from Mendeley to Zotero. I first had to downgrade Mendeley because recent releases also encrypt your local database to guarantee lock-in [1]. Quite scary.
I'm very glad I never even tried Mendeley given the database encryption fiasco. Mendeley put a blog post out saying that preventing importing to Zotero was unintentional, but I don't buy it.
https://blog.mendeley.com/2019/01/31/the-importance-of-inter...
Before the database encryption fiasco, I would recommend Mendeley and Zotero if someone wanted a citation manager, but now I recommend staying away from Mendeley as much as possible.
The only major problems I've had with Zotero were related to Firefox's switch to WebExtensions. Now adding a copy of a webpage to a citation is more difficult than before the switch, though probably equally difficult as in Mendeley.