Granted, I've not professionally used slack so I can't say if it's much better.
- Teams integration with outlook is the best. Makes meetings with remote team members really slick.
- Teams video chat (at least for a smaller group of people) is way better than solutions like zoom. It's just super convenient to be able to do a video or voice call with someone to work something out.
- The ability to create small group chats with people on the fly is awesome. When we need a 1 off async convo with the right people it's easy enough to just add them to a chat, name it something useful, and be off.
- Because video chat has a chat, it's pretty easy to do a message where you can write something without interrupting the current conversation. That also doesn't go away as soon as the meeting ends (ala zoom).