Teams works great for meetings and sucks for chat and persistent chat. I never use Slack for calls, I use it for IMs.

Teams has problems with its UI, organizing teams/channels, notifying, and basic always on functions. At least every other day, Teams secretly signs me out and I’m offline until I try to do something and sign in again, just to get IMs and missed calls. That has never happened with Slack.

Also Teams/SharePoint sucks so hard for web site and doc collaboration. Search doesn’t work well and it’s hard to get users organized around content. I’d rather have a shared Word doc than a Teams site.