Faster. Discord is lighter and faster.
Simpler. I don't need comments and threads and snippets and posts at the expense of simple communications. These features are also inconsistent and incompatible across devices.
Search/Cost. Search doesn't search contents of snippets which was a gotcha. And with a 10000 message limit, anyone using it for free reaches a point where search breaks. I was deleting messages for a while because at the end of the day all the 50/mo would have gotten us is unbroken search. It's like 99% of the product is free and they ask to pay 50/mo for the last 1%.
Web Hooks. Integrating anything is as simple as a single line cUrl command. So for business use, if you already have a server doing a bunch of stuff with various APIs, adding notifications to discord is a one liner.
Also Discord has a more intuitive server list on the side bar. With slack you have to register with every team and "switch". In Discord it's just another tab.
A business on Slack is one that 1) can't see a superior chat program when they see one, 2) are willing to pay for an inferior product, and 3) can't look past the "gamer" origins of a platform.
But to Slack's credit, they built a business out of just chat, which is miraculous. And though I've arrived at Discord, they deserve all the credit and respect in the world for achieving what they have achieved through a mere chat subscription service. And I'm sure their philosophy and business direction is what got them to where they are, so standing up and challenging exactly that would admittedly be naive on my part. However I still do not believe any of the points that I have made are incorrect either, which just tells you more about this industry (chat industry?).
They just need a "Discord for Business". They would kill.