Are you talking about Microsoft Teams? Because I hate Microsoft but Teams blows Slack out of the water by a country mile in terms of usability, reliability, and resource usage. I can't get a basic voice call working in Slack for longer than 45 seconds Teams conversely has smooth, reliable video delivery.
All in all I think Discord is better than either of them but I'll take Teams over Slack any day.
I admit the voice/video chat in teams is really well done. But that's because they are using Skype's technology for that. But the actual interface, messaging, and overall experience of Teams is really bad. Just yesterday I wasn't able to do a cmd+a to select all the text in my message box. It's a clunky and annoying daily experience
All in all I think Discord is better than either of them but I'll take Teams over Slack any day.