If you're running a company under 50 people, you'll hear that Slack and Microsoft Teams are interchangeable. They're not. Both are mature, stable platforms, but they're built on different assumptions about how work happens—and for a small team, that difference matters more than you'd think. This is not about which one is objectively better. It's about which one actually fits how your team works, what you're already paying for, and whether you want chat embedded in a broader ecosystem or standing alone. The core trade-off: focused tool vs. ecosystem play Slack is a chat platform. That's it. It does chat extremely well, has a huge app marketplace, and forces you to make a conscious choice about every other tool you layer on top. Teams is part of Microsoft 365. If you're already paying for Office (Word, Excel, Outlook, OneDrive), Teams comes bundled in. It sits in the same product family as your email, files, and video calls. You don't choose to add it; it's already there. For a small company, this matters. If you're a tech-forward startup using Google Workspace, Slack feels natural. If you're a professional services firm, contractor, or consulting business that lives in Outlook and Excel, Teams feels inevitable. Pricing: the hidden advantage of bundling Slack's pricing is simple and transparent: $8 per user per month (Pro plan) for most small teams. You pay per active user, and there's no volume discount for 10 people vs. 40 people. Teams' pricing is buried in Microsoft 365. For a 25-person team: Microsoft 365 Business Basic (email, Teams, Office online): $6 per user/month Microsoft 365 Business Standard (Basic + full Office desktop apps): $12.50 per user/month Here's the catch: most small professional services firms and agencies already pay for Office. They're using Word for contracts, Excel for budgets, Outlook for email. For them, Teams costs $0 extra. It's already in the bundle. If you don't use Office and never will, Slack's $8/user is cheaper than paying $6+ for Microsoft 365 just to get Teams. But if you use even two Microsoft apps regularly, Teams becomes the economic choice. At 25 people: Slack costs $200/month. If your team uses Office, Teams is included in your existing $6–$12.50/user Microsoft 365 spend. That's $150–$312, but you're already paying it for email and docs. Integration and ecosystem fit Slack has roughly 2,500 verified apps in its marketplace. Want to pull CRM data into chat? Connect invoicing notifications? Link your project management tool? Slack has integrations for nearly everything, and if it doesn't, Zapier or Make can stitch things together. Teams integrations are more limited. Microsoft prioritizes its own ecosystem (Power Automate, SharePoint, Dynamics 365) but also supports common third-party tools like Salesforce, Jira, and GitHub. The integration experience is generally deeper within the 365 family—e.g., pinning an email to a Teams channel, or embedding a live Excel sheet—but sparser outside it. For a small team using a CRM , invoicing platform , or other specialized software, Slack's breadth of integrations is a real advantage. If you're mostly using Office, SharePoint for file sharing, and maybe Salesforce, Teams integrates more smoothly with what you already have. Ease of use and onboarding Slack is intuitive for anyone who's used a messaging app. Channels, direct messages, reactions, threading—it's all familiar. The learning curve is near-zero, and onboarding a new hire takes minutes. Teams is equally intuitive, but it has more surface area. Teams, Channels, Chats, Files, Calls, and Meetings are all distinct concepts. For a first-time user coming from Slack, it can feel scattered. For someone coming from Outlook and SharePoint, it feels like a natural extension of what they already know. Both platforms are stable and reliable. Neither has a meaningful uptime or performance advantage at the 50-person scale. Mobile experience and working remote Slack's mobile app is genuinely good. Notifications are reliable, search works, and the experience on iPhone or Android feels like a full product, not a compromise. Teams' mobile app is competent but heavier. Notifications can be spotty, and search is slower. For field teams or remote-first companies where mobile is the primary interface, Slack's mobile experience is noticeably better. If your team is mostly at desks and uses mobile as a secondary channel, the difference is negligible. If your team is distributed or includes field staff, Slack's mobile experience gives it a real edge. Who should choose what Choose Slack if: You're already in Google Workspace (Gmail, Docs, Drive). You use a diverse set of specialized tools (CRM, invoicing, project management, etc.) and want easy integrations. Your team is remote or frequently mobile. You want a chat tool that does one thing extremely well without forcing you into a larger ecosystem. You have a technical team that values app extensibility and automation. Choose Teams if: You're alre