Slack leads messaging core 6.5 to 2.5, encryption and access 5.3 to 2.3, governance and discovery 5.5 to 2.5 and sovereignty 2.8 to 0.7 — each a six-to-zero lean for Slack — and integrations 5.8 to 3.8, five judges leaning Slack with one tie. Microsoft Teams (Chat) is ahead on pricing transparency alone, 4.0 to 3.7: three judges lean Teams, one leans Slack, two tie, and its verdict cites add-on prices published exactly — Teams Premium at 8,70 € per user per month, VAT excluded — where the Slack verdict records no per-user price, leaving the annual invoice not computable. Deployment control nearly ties, 1.0 to 1.3, four ties and two judges leaning Slack. The listed sovereignty attributes match on IE jurisdiction, US by default residency and US CLOUD Act reach exposure, with ownership unknown for Teams and foreign-controlled for Slack. Persona-weighted totals span 1.8 to 3.3 for Teams and 4.0 to 4.9 for Slack.
Choose Microsoft Teams (Chat) if
You must compute the annual invoice before signing — pricing transparency leans Microsoft Teams (Chat) three judges to one, with add-on prices published exactly, while the Slack verdict records no per-user price and an annual invoice that is not computable.
Your finance approval needs exact public per-user prices — Teams Premium at 8,70 € per user per month and Microsoft 365 Copilot Business at 18,20 € per user per month, VAT excluded, are published.
Your vendor policy screens out foreign-controlled ownership — the sovereignty attributes list Slack as foreign-controlled and record Microsoft Teams (Chat)'s ownership as unknown.
Your evaluation weights published pricing most heavily — pricing transparency is the one criterion where Microsoft Teams (Chat) leads on means, 4.0 to 3.7, and on leans, three judges to one.
Choose Slack if
You weigh messaging core first — it leans Slack six judges to zero, mean 6.5 to 2.5, credited for channels, Slack Connect cross-organisation rooms, AI search over stored knowledge and unlimited message history from Pro.
Your security review scores encryption and access heavily — that criterion leans Slack six judges to zero, mean 5.3 to 2.3.
You must run retention, legal hold and DLP — governance and discovery leans Slack six judges to zero, mean 5.5 to 2.5.
Your platform engineers want a buildable surface — integrations leans Slack five judges to one tie, mean 5.8 to 3.8, with the platform engineer crediting 1.7 million weekly active apps.
You need Germany data residency — sovereignty leans Slack six judges to zero, mean 2.8 to 0.7, and the verdict records Germany residency purchasable from Business+.
Read this comparison as one judge. Each weighs the same scores by what they care about.
The Skeptic
Reads for the message-history cap, the tier where SSO appears, and what "unlimited" excludes. Has seen "end-to-end encrypted" mean direct messages only, on request, with search disabled — and wants that sentence found rather than assumed.
Microsoft Teams (Chat)
Slack
This judge's pick
Criterion by criterion
Channels, threads & search
Microsoft Teams (Chat)
The captured pages name chat and channels as one of the product's solution areas, which is a category heading rather than a capability; we found no public information on threading, mentions, search across message history, or any documented history limit.
Slack
Channels, Slack Connect cross-organisation rooms with admin-controlled connection policy, AI search over stored knowledge, and — credit where due — a legible history cap: one year on Free, unlimited from Pro. But the words 'thread', 'edit history', 'pinned' and any human-readable export of a conversation appear nowhere in this registry, so I stop short of the 8 anchor.
Encryption & access control
Microsoft Teams (Chat)
Encryption of meetings, chats, calls and files is listed as included with no stated mechanism, and we found no public information on transport versus at-rest encryption, key custody, end-to-end encryption, per-channel roles, or guest scoping. The privacy statement does say that time, date and participants of communications are recorded and that data can be used to develop and train the vendor's AI models.
Slack
Encryption at rest and in transit with the vendor holding the keys, plus SAML SSO down to Free, 2FA, information barriers and an Enterprise Key Management add-on — key custody you can rent, not E2EE. There is no end-to-end encryption and no sentence stating what the vendor itself can read anywhere in the evidence, and silence on that is the finding.
Retention, discovery & co-determination
Microsoft Teams (Chat)
The only governance statements are that data security and compliance sit in the Purview Suite requiring Microsoft 365 E3, and that all associated data is deleted on cancellation — pointers rather than a documented regime. We found no public information on per-channel retention, audit logs, discovery export, or admin control over activity analytics.
Slack
Retention configurable at workspace and channel level (plan-dependent), legal hold, audit logs and native DLP on every plan — real governance bones. But no discovery or export format is documented in any form, and nothing says whether presence or activity analytics can be switched off — the archive as a legal object is half-built in this evidence.
Deployment & data custody
Microsoft Teams (Chat)
The captures show cloud subscriptions for 1–300 users, billed and cancelled through the Microsoft 365 Admin Center; we found no public information on a self-hosted edition, a private-cloud option, or a documented export format. The only exit-related statement is deletion of all associated data on cancellation.
Slack
Cloud-only SaaS: the entire registry is tier pricing, and the one 'private cloud' sentence is Slack's own AWS private cloud for their LLMs, not a customer deployment option. No self-hosting, no open-source core, and no export path documented at all — even the anchor-3 bar of a documented full export goes unevidenced, and Germany residency from Business+ changes where the vendor holds your archive, not who holds it.
Integrations & extensibility
Microsoft Teams (Chat)
Over 250 integrated business apps are stated, chatbot building with Copilot Studio is included in the business plans, and agents run on a consumption-priced Azure subscription. We found no public information on a documented API, webhooks, rate limits, or a sandbox, so this reads as native integrations plus a vendor-run bot builder.
Slack
Named integrations, 1.7 million weekly active apps, automation 'mit einem Klick oder per Code', SCIM provisioning, SSO, and per-workspace control over third-party services. What's missing for the next anchor: any documented API surface, rate limits, sandbox or deprecation policy — this sheet evidences an ecosystem, not a documented platform.
European sovereignty
Microsoft Teams (Chat)
The vendor is a United States corporation whose privacy statement says personal data may be stored and processed in the user's region, in the United States, and in any other jurisdiction where the vendor or its service providers operate, with EU-US framework participation as the transfer safeguard. We found no public information on a guaranteed EU hosting option or a published subprocessor list.
Slack
The vendor is Salesforce, Inc. of San Francisco, and the pipeline could confirm neither contracting entity, ownership, default residency nor a single subprocessor on the captured pages. The one European fact — 'Datenstandort Deutschland' — starts at Business+, making EU custody an upsell, and the LLMs sit in Slack's AWS private cloud of unstated region.
Pricing transparency
Microsoft Teams (Chat)
Add-ons are priced precisely — Teams Premium at 8,70 € per user per month and Microsoft 365 Copilot Business at 18,20 € per user per month (discounted 15,60 €), annual billing with automatic renewal, prices excluding VAT — but we found no public information on per-user prices for the base plans themselves. Compliance data protection sits in a Purview Suite gated behind Microsoft 365 E3, unpriced here, and the Copilot discount applies to the first year and to existing business customers only.
Slack
The tier boundaries are unusually legible — unlimited history from Pro, SAML SSO from Free, DLP on all plans, Germany residency from Business+, EKM as an add-on — but the registry contains not a single per-user price, billing period or VAT treatment. Without a number anywhere, the annual invoice is not computable from this evidence, so I score below the 'headline exists' anchor despite the good feature-to-tier mapping.
Sovereignty, side by side
Dimension
Microsoft Teams (Chat)
Slack
Legal entity
Not determined
Not determined
Ownership
Not determined
Not determined
Data residency
Not determined
Not determined
Subprocessors
Not determined
Not determined
Facts, side by side
Only facts both products carry under the same definition — anything else would not be a fair row.