I was going to comment that teams doesn't have threads and slack may still win long term, but turns out teams added threads in the last couple of months(1). So yeah.

1: https://techcommunity.microsoft.com/blog/microsoftteamsblog/...

I'll vouch for this. I moved from Slack to Teams and Teams is clearly an inferior product. That said, I don't think SalesForce owning Slack is really a big improvement.