Although I'm not sure how it compares to YNAB since I've heard good things about it too. What I like about Monarch is the nice UI, no ads, responsiveness and that the sync doesn't fail (often) like it failed (often) with Mint all the time.
I like that it has investment tracking as well.
Agreed that mint was terrible with syncing. I don't know if it's improved at all in the last several years.