Slack Review 2026: The Connective Tissue Every Other Tool Plugs Into

How we tested this Last tested: March 2026 (vBusiness+ (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 honest framing before you read this review

You’re evaluating Slack in 2026. That means one question matters more than any feature scorecard: which consolidation wave is your company in?

If your CFO stares at your Microsoft 365 E3 invoice (£18.10/user/month) and sees “Teams included,” the long-run answer is Teams. Not because Teams is better — it isn’t on UX, threading, or search. But because buying a 50-seat Slack contract in a Teams-mandated company is a doomed two-year fight that ends in migration anyway.

If you’re not in that situation, read on. Slack is still the strongest connective tissue in the B2B SaaS ecosystem. The question is whether “connective tissue” is worth £6.75-£12.50/user/month when your PM tool is already shipping chat features.

What we tested

We ran Slack Business+ (£12.50/user/month) on a 25-seat synthetic workspace for six weeks in Q1 2026. We tested:

• Channel discipline: how naturally do teams organise communication vs defaulting to DMs?
• Thread behaviour: do teams actually use threads, or does every reply become a new message?
• Huddle quality: audio/video call experience in a distributed team context.
• Integration breadth: how many of the 2,400+ app integrations actually work without configuration pain?
• Search: finding a specific conversation from 3 months ago.
• Mobile parity: iOS + Android experience vs desktop.

We also ran the same 25-seat workspace on Microsoft Teams for direct comparison. Teams review is here.

The integration advantage is real

This is where Slack earns its price. We integrated it with:

• Notion (document updates surfaced in channels — works flawlessly)
• Linear (engineering issues → Slack channel via Zapier — 15-minute setup)
• GitHub (PR notifications → #engineering — standard Slack app, no config pain)
• Loom (video shared in channels with preview — native integration)
• PagerDuty (on-call alerts — the use case that makes Slack irreplaceable for infrastructure teams)

The pattern: every time we wanted to connect two tools in the stack, Slack had a first-party or well-maintained third-party app for it. Teams has a similar marketplace but the app quality is more variable and the configuration friction is higher.

The real claim: if you have 5+ SaaS tools and you don’t already pay for M365, Slack becomes the hub that makes everything else work better. That’s not a feature — it’s a network effect.

Pricing: what you actually pay

The marketing-page floor is £6.75/user/month (Pro). Here’s what most real teams pay:

Plan	Price	Who actually needs this
Free	£0	1-10 people, willing to lose message history after 90 days
Pro	£6.75/user/month	10-50 people, don’t need SSO
Business+	£12.50/user/month	Any team that needs SSO/SAML or audit logs
Enterprise Grid	Custom (est. £25+/user)	Org-wide compliance, data residency, eDiscovery

The SSO tax here is significant: SAML/SSO is Business+ only. If your IT team requires SSO — and they will once you’re past ~50 people — the floor jumps from £6.75 to £12.50. That’s where the Slack vs Teams cost maths start to favour Teams in M365 shops.

What the free tier actually gives you

Free Slack: up to 90 days of message history, 10 app integrations. For teams under 10 people with simple stacks, this is workable. For anything above that, you’ll hit the 90-day wall by month 3 and regret not being on Pro from day one.

The 10-app integration limit on free is the real constraint: if you connect Notion, GitHub, Google Calendar, and your project management tool, you’re already at 4. The moment you add a notification bot or a monitoring tool, you’re bumping into it.

Slack vs Teams: the honest comparison

We ran both for six weeks in parallel. The findings:

Slack wins:

• Threading: Slack’s threaded conversations are genuinely better. Teams threads are confusing — replies can live in the channel or in the thread, and the distinction isn’t always clear.
• Search: Slack’s search is faster and more accurate, especially for older messages.
• App ecosystem: 2,400+ apps vs Teams’ marketplace. Quality and consistency are higher on Slack.
• UX: Just better. Less cognitive load to learn. Engineering teams specifically hate Teams’ UX — this is a real talent-retention consideration.

Teams wins:

• Cost in M365 shops: zero incremental cost if you’re on E3/E5.
• Compliance: Purview integration, eDiscovery, legal hold tooling is superior.
• Video calls: Teams’ meeting experience (scheduling, recording, transcription) is better than Slack huddles for anything formal.
• SharePoint integration: if your company lives in SharePoint, Teams surfaces that content naturally.

The verdict: if you’re not in an M365 shop, Slack wins. If you are, the honest answer is Teams — and we say that as a site that earns affiliate commission on Slack.

The realism caveat

“If a 15-person team onboards Slack properly — one named workspace owner, a channel structure that’s actually agreed on before day 1, and a 2-week grace period to kill off DM habits — the typical result is 2-3 fewer status-check meetings per week. At £600/month average IC cost, that’s £400-600/month in recovered time. If you just add Slack on top of email without doing the channel hygiene work, you’ll add noise and the team will hate it within 60 days.”

This is the make-or-break factor. Slack is not a self-organising tool. It amplifies whatever communication habits your team already has — good or bad.

Pros and cons

What works:

• Integration breadth (2,400+ apps — no competitor comes close)
• Search quality — finding that conversation from 6 months ago is actually feasible
• Slack Connect for external client communication (cleaner than email chains)
• Huddle quality for quick informal calls
• Mobile apps are genuinely good

What doesn’t:

• Free tier’s 90-day history limit will bite you
• SSO requires Business+ — the jump from £6.75 to £12.50 is jarring
• No native task management (you’re paying for Slack + a PM tool)
• Not competitive in M365 shops — the integration advantage disappears when Teams has M365 native

Pricing for 25 seats: three scenarios

Scenario	Slack cost	Teams cost	Recommendation
BYO stack, need integrations	£312.50/mo (Business+)	N/A	Slack
M365 E3 shop	£312.50/mo	£0 incremental	Teams
Compliance-heavy, 100+ seats	£750+/mo (Grid)	Bundled in E5	Depends on tech debt

Final verdict

Slack earns its 9.1/10 for teams that aren’t already locked into Microsoft 365. The integration ecosystem is the moat — when your stack has 5+ tools and you want them all to surface notifications and updates in one place, nothing else competes at this price point.

The hard truth: if your CFO is about to sign another E3 renewal, have the Teams conversation before renewing Slack. We’ll still send you to the affiliate link, but the honest answer is that a Teams-mandated company should run on Teams, not Slack.

Start the free trial if: you’re not in an M365 shop, your team uses 5+ SaaS tools, and someone will own the workspace setup.

Don’t start the trial if: your IT mandate includes SSO on a budget under £12.50/user, or your company is heading toward M365 consolidation in the next 18 months.

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