I joined Vocal before I joined Medium. I'll be straight, I like Medium better as a source of steady-ish income. You're absolutely right about Grammarly being an issue, it shows errors, but you can't click and correct.

It's also difficult, at least for me to get enough reads to get any money. PS: there's a $50 bonus upon publishing your 50th story.

I use it, honestly, just for challenges now. I've won 2 and was shortlisted for the Fiction Awards which gives me a year of Vocal + for free, so I'm on the plus side thus far. And I do like that they pay for external reads. Tips are nice and I do find there's a very supportive and active Facebook community, which is cool.