Slack is widely praised for its user experience. The channel organization, threading, emoji reactions, and overall design feel intuitive and enjoyable to use. Notifications are well-controlled, the search function is fast and comprehensive, and the mobile apps are excellent. New employees typically learn Slack within hours.

Microsoft Teams has improved significantly but still feels heavier and more complex than Slack. The Teams/Channels/Tabs architecture can be confusing for new users, and the interface tends to feel cluttered with features. However, for organizations already using Microsoft 365, the familiarity of the Microsoft design language helps with adoption.

Slack's huddle feature (voice and video calls) is good for quick check-ins but is not designed for large meetings or webinars. You can screen share and have small group video calls, but for formal meetings or all-hands calls, most Slack users rely on Zoom or Google Meet for the heavy lifting.

Microsoft Teams has much more powerful video conferencing — it was designed as a full Zoom competitor. Teams meetings support hundreds of participants, live captions and transcription, breakout rooms, recording to SharePoint, and live events. For organizations that conduct formal meetings, webinars, and all-hands presentations, Teams' built-in meeting capabilities are excellent.

Slack's free plan limits message history to 90 days, which is its biggest complaint. The Pro plan at $7.25/user/month is reasonable, but for a company of 100 people, that's $8,700/year just for messaging. Slack's pricing becomes a meaningful line item, especially when compared to Microsoft's bundling strategy.

Microsoft Teams has a significant pricing advantage. It is included in every Microsoft 365 Business subscription ($6–22/user/month), which most organizations already pay for email, Office apps, and OneDrive. For companies already on Microsoft 365, Teams is essentially free. This bundling advantage is why Teams has overtaken Slack in total user count.