As someone who uses both I still contend that Slack is superior. The messiness seems to come from too many channels being made and needs to be actively pruned by management and company practices around Slack need to be communicated to employees.

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.

Good point, teams video calls seems better; Slack video was a late addition.

The Slack-using employer also used Zoom. MS is the all-in-one in this regard too.

It's extremely easy to argue that Slack is much better than MSTeams, but now the market does not exist for anyone who wanted to make something better than Slack.