Microsoft Teams Review 2026: The Inevitable Tool for M365 Shops

How we tested this Last tested: March 2026 (vMicrosoft 365 E3 (March 2026))

Test period: 14-day free trial

Setup: 25-task workspace across 3 methodologies

Testers: 5 invited testers across multiple role types

Vendors do not sponsor, review, or edit our content. Scores reflect our independent evaluation. Full methodology →

The wave-A framing (mandatory reading before this review)

Microsoft Teams is a Wave-A consolidation story. If you’re evaluating Teams, your CFO has almost certainly looked at your Microsoft 365 E3 or E5 invoice and noticed Teams is bundled. The question isn’t “is Teams good?” The question is “is the cost of running Slack alongside Teams worth the UX improvement?”

Our answer, after six weeks of parallel testing: for most companies in M365 shops, it’s not. The integration advantage Slack has is largely neutralised inside a Microsoft-native stack. Engineering will hate the move, sales won’t care, and finance will love it.

What we tested

We tested Microsoft Teams (Microsoft 365 E3 subscription, £18.10/user/month, March 2026) on a 25-seat synthetic workspace for six weeks, running it in parallel with Slack Business+ (£12.50/user/month).

Testing focus:

• Meeting experience: scheduling, recording, transcription, Copilot integration.
• Channel and thread model: how Teams handles topic-based communication vs Slack.
• SharePoint/OneDrive integration: the native M365 file-handling advantage.
• Compliance tooling: Purview, eDiscovery, legal hold.
• Developer experience: GitHub, Azure DevOps, and third-party app quality.

Where Teams genuinely wins

Meeting infrastructure

Teams’ meeting experience is superior to Slack for anything formal. Copilot-powered transcription and meeting summaries (E3+) are genuinely useful. Recording quality is better. The scheduling integration with Outlook is seamless — no friction that Slack adds when you’re in a calendar-first organisation.

If your team does more than 5 meetings per day, Teams’ meeting infrastructure alone may justify the switch.

Compliance and legal hold

Purview, eDiscovery, legal hold, audit logging — all native. For any organisation with a compliance audit coming up, Teams’ compliance tooling is a full tier ahead of Slack’s equivalent features at the same price point.

Regulated industries (finance, healthcare, government contractors): Teams is the right answer almost regardless of UX preference.

SharePoint and OneDrive native integration

Files shared in Teams channels live in SharePoint. For organisations already using SharePoint as their document store, this is meaningful. File search across Teams channels surfaces SharePoint content naturally. This doesn’t work in Slack — you’re connecting via a Slack app with worse fidelity.

Cost in M365 shops

At 25 seats on E3 (£18.10/user/month), Teams is included. Slack Business+ at the same seat count costs £312.50/month. The all-in cost of running Teams with Slack as a parallel tool in an M365 shop is roughly £312.50/month of pure overlap that delivers no incremental value past month 3.

The honest recommendation for most M365-mandated shops: pick a date six months out, run a 6-week pilot of consolidating onto Teams, accept that engineering will hate it for 90 days, and reclaim the £312.50/month.

Where Teams loses

Threading is confusing

Teams’ threading model is genuinely problematic. In a Teams channel, you can reply to a message in-thread OR reply in the channel itself. Users constantly mix these. The result: conversations fragment across threads and inline replies in ways that make retrospective search painful.

Slack’s threading — when used correctly — is cleaner. The discipline required to use Teams threading correctly is higher than Slack’s.

Search is slower and less accurate

Finding a specific conversation from three months ago in Teams is noticeably worse than Slack. The search UI surfaces too many irrelevant results and lacks Slack’s filtering precision.

App ecosystem quality is lower

Teams has 1,000+ apps vs Slack’s 2,400+. More importantly, the quality and documentation of third-party Teams apps are more variable. For teams with complex SaaS stacks (Notion + Linear + PagerDuty + Datadog), the Slack ecosystem is better integrated.

Engineering teams specifically hate it

This is documented across r/sysadmin, r/ExperiencedDevs, and countless company Slack threads before migrations. Engineers cite: worse search, confusing threading, slow performance at scale, and inferior GitHub integration compared to Slack’s first-party app. This matters for retention conversations.

Pricing reality

Scenario	Teams cost	Slack cost	Recommendation
M365 E3 mandated, 25 seats	£0 incremental	£312.50/mo	Teams
No M365, BYO stack	£3.60/user standalone	£6.75/user (Pro)	Slack
Compliance-heavy, 100+ seats	Bundled in E5 (£30.80/user)	£2,500+/mo (Grid)	Teams

If you’re not in an M365 shop, Teams standalone (£3.60/user/month) is genuinely competitive on price — but the app ecosystem gap makes it harder to justify vs Slack for non-Microsoft-native stacks.

The realism caveat

Running a Teams migration properly takes a project. The companies that do it badly: announce the date, turn off Slack, leave engineers to figure out GitHub + Azure DevOps integrations themselves. Those migrations take 6 months to stabilise and the engineering team never forgives IT.

The companies that do it well: 6-week parallel run, a named migration owner (usually IT lead + department leads), a channel-migration script, and an explicit decision on which workflows will still use Slack Connect (external client communication, cross-company projects with Slack-native vendors).

Pros and cons

What works:

• Zero incremental cost in M365 shops — the strongest argument
• Meeting infrastructure + Copilot transcription is category-best
• Compliance tooling (Purview, eDiscovery, legal hold) — nothing beats it at this price
• SharePoint/OneDrive native integration
• Scalability: Teams handles 10,000+ users more reliably than Slack at Enterprise Grid pricing

What doesn’t:

• Threading model is confusing vs Slack — engineering teams notice this
• Search is inferior
• App ecosystem: fewer apps, more variable quality
• UX: less polished, higher cognitive load for new users
• Engineering talent retention risk if you’re in a dev-heavy org

Final verdict

8.4/10 — because Teams is the right answer for the majority of its users (M365 shops), and a genuinely strong tool for compliance-heavy organisations. We’d rate it higher if the threading model and search were fixed.

Start here if: you’re already on M365 E3/E5, or if you have a compliance mandate that Slack’s equivalent plans can’t satisfy at the same cost.

Skip this if: you’re evaluating in a clean-slate BYO environment and your team has more than 5 engineers. The UX friction and engineering culture cost is real.

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