As a product, I like Slack a lot more than teams. Chatting is easier, the apps are better, reminders and scheduled messages, workflows, etc. Threaded conversations are much easier as well, and aren't artificially restricted to certain types of channels.

At a high level though, Salesforce is often seen as a predatory company. Prices are high and they will squeeze their users for every nickel (as demonstrated here). They will also monetize your data in ways that you probably don't want.

Teams chat is pretty bad, I agree. But it does have these benefits:

  - Free if you're already in the Microsoft ecosystem, which most companies are.
  - Microsoft is probably a better steward of your data.
  - Teams video / audio calls are much much better than Slack huddles.
  - That's pretty much it tbh

I didn't make the decision, the company I worked for did. I was asked to come up with a way to help make the process smooth.

I don't know their exact reasons, probably budget related since they were already using O365.

I can nearly guarantee it wasn't because Teams offers a better user experience. :D