One factor for Teams (vs Slack or others) may be regulatory requirements (eg HIPAA). A quick perusal came down to "Slack Enterprise can be made HIPAA compliant"

One factor for Teams (vs Slack or others) may be regulatory requirements (eg HIPAA). A quick perusal came down to "Slack Enterprise can be made HIPAA compliant" where I got the impression that Teams was a lot closer out of the box.