I use the free version of both, even though I don’t much like either. Grammarly makes me think I’m wrong about something I wrote correctly and I waste time trying to resolve my doubts before leaving what I wrote alone. I use it only because it sometimes catches typos. I have to turn it off when I edit or write work on HubPages because HubPages doesn’t allow its use.
I am giving Hemingway a try. It does spank my hands when I write an unclear sentence. But if I followed all its suggestions, it would stifle what’s unique about my writing voice. If we all let it dictate to us, pretty soon we’d all sound alike on Medium.