When I changed from a Slack-using employer to a MS Teams-using employer around 2 years ago, I found it impossible to argue that the usability of MS Teams was even close to the usability of Slack. Slack was significantly better in this regard.
MS Teams had better integration with some other MS services such as OneDrive. That's obviously going to be so, that's what it's for.
We use Slack for text comms and Teams for video meetings. Seems like a decent balance, Slack video calls seems very unpolished compared to the Teams video experience.
MS Teams had better integration with some other MS services such as OneDrive. That's obviously going to be so, that's what it's for.