Mattermost vs Sierra Comparison

Why choose Mattermost

• Has a free plan (Sierra does not)
• Higher Cost score (5/10 vs 2/10)
• Higher Security score (10/10 vs 9/10)
• Better fit for government (9/10 vs 4/10)
• Better fit for small business (4/10 vs 1/10)

Why choose Sierra

• Higher Analytics score (8/10 vs 3/10)
• Higher Support score (8/10 vs 6/10)

Mattermost

Pros

• Can be fully self-hosted or air-gapped, which suits defense, government and regulated industries
• Enterprise tiers include strong compliance tooling: FIPS 140-3 builds, legal hold, compliance export and granular RBAC
• Playbooks give incident and DevOps teams repeatable checklists with automated triggers inside chat
• Built-in Jira, GitHub and GitLab integrations, plus an open API for custom bots
• Open-source core under MIT and AGPL licenses avoids full vendor lock-in

Cons

• The Boards kanban plugin is in maintenance mode and has been removed from the in-product marketplace
• Since v11 the free Entry plan shows only the last 10,000 messages and Team Edition is capped at 250 users, which drew community criticism
• The vendor publishes no prices, licenses are annual prepaid only, and every server needs its own license
• No Gantt charts, time tracking or project reporting, so it cannot replace a dedicated project management tool
• Self-hosting requires admin time and server upkeep

Sierra

Pros

• Outcome-based billing means customers usually pay only for resolved conversations or other agreed results, not for each seat.
• Three build options cover both CX teams and engineers: the no-code Agent Studio, the code-first Agent SDK, and Ghostwriter for building agents from SOPs.
• One agent runs across chat, voice, SMS, WhatsApp, email and ChatGPT, keeping context between channels.
• Its list of compliance attestations is broad, covering SOC 2, ISO 27001, ISO 42001, HIPAA, PCI DSS and FedRAMP.
• It has a strong roster of enterprise customers, including SiriusXM, ADT, Rocket Mortgage and SoFi.

Cons

• There is no public pricing, and competitor estimates put annual contracts at about $150,000 or more.
• There is no self-serve or trial tier, so small teams cannot try it on their own.
• Implementation is largely vendor-led, which can make customers depend on Sierra's team for changes.
• There are few public reviews (7 on Gartner Peer Insights) to verify claims against.
• Some reviewers say voice quality still falls short of human level, and that complex telephony setups depend on how far the integration goes.