Discord's role/permission management is incredibly powerful. There's a couple things I'd love to see to make it a bit easier to use (duplicating/copying permissions between roles would be great), but I'm comfortably using it for a public Discord channel with 300+ members and growing[1] and I can actually visualize how to keep the chat functional if the member count grows by 10x.
I strongly recommend Discord over Slack for public chat groups; I'd happily use it over Slack for company chat as well, with the caveat that the integration/app story isn't quite as far along as Slack is.