One thing I think Teams does well in this space, and where I feel Slack falls short, is the organisation of channels.

With Teams you can put people in... well teams, and each team has channels and other data associated with it. This hierarchy makes it easy for people to keep a multitude of channels and data organised without actually having to do it themselves.

Another thing I have to (begrudgingly) concede to Teams is that it's essentially "free" and from the perspective of an exec it does the same thing as Slack + has better video conferencing. Even simple things like meeting with 3rd parties is very easy to do on Teams - just send an invite. Whether or not the A/V actually works during the call or peoples PC's don't run out of memory mid-meeting is another matter, but on paper it looks good.