* In MS teams, I can create conversations, group chats, organic meetings, and add people (and include history) as I want and desire. I prefer it for quick discussions with my colleagues and to get a rapid problem solving or critical incident conversation where I don't immediately know who I need / what it's about, and it'll scale as I add people. I push a button and talk to people, push a button to add people, push a button to video chat, all seamless.
* Slack is structured and formal and based around enterprise-created channels and workgroups, with way too much noise in each massive channel and way too little content that's even remotely relevant to me. Outside of channels, conversations are horribly gimped: A) I can only have one conversation with each set of people, I cannot simply rename a chat and have three different chats with same people around different topics B) If I add people to an existing conversation, it will create a new chat without history (this may have improved recently as I know we sent a TON of feedback to Slack admins). Basically, to get anything done you have to create channels, which is great for "top down, I know ahead of time what I need / want to enforce" structure, but awful for "this started as a one-on-one and is now a massive discussion with 17 people"
I'm looking at some of the other comments, and it seems they have some weird gimped version of MS Teams. E.g.:
>>"Allow “create a meeting for this Teams channel” that puts any meeting chat directly in the channel."
This... is how it works for me. I start a conversation with some people, then I add people, then I click "Call", then we all video call together, then we are done and keep typing in it, repeat as needed.
Weird!