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Plain vs Sierra

Features, pricing, ratings, and pros and cons, side by side.

Plain logo

Plain

AI-powered support platform for B2B teams, unifying Slack, email and chat in one workspace

Free trial
Visit websiteView details
Sierra logo

Sierra

Enterprise AI agents that handle customer conversations across voice, chat and messaging, priced by outcome

Paid
Visit websiteView details

Verdict

Plain is listed under Help Desk Software and Sierra under AI Customer Support. Plain scores higher in FinderAtlas's editorial review (7.9 vs 7.6 out of 10), led by ease of use and value for money. Neither has a free plan. Only Plain offers an API.

Best overall

Plain

  • B2B SaaS companies
  • Support teams
  • Customer success teams
  • Startups

Choose Plain if

  • You want a tool built for Teams that support business customers through shared Slack or Teams channels and want AI triage, routing and an API-first setup.
  • Built around B2B support, with Slack, Teams and Discord channels alongside email and chat.
  • Ari and Sidekick AI agents are included from the entry plan.

Choose Sierra if

  • You want a tool built for large companies automating high-volume customer conversations across voice and digital channels with outcome-based pricing.
  • Outcome-based pricing ties cost to results rather than seats or tokens.
  • Covers voice, chat, SMS, WhatsApp, email and ChatGPT from one agent build.
Best for beginners
Plain
Best for business
Sierra

Features

18 features compared.

  • Multichannel Inbox
    Plain
    Available
    Sierra
    Not available
  • Ari AI Agent
    Plain
    Available
    Sierra
    Not available
  • Sidekick
    Plain
    Available
    Sierra
    Not available
  • Workflows
    Plain
    Available
    Sierra
    Not available
  • Insights
    Plain
    Available
    Sierra
    Not available
  • Bring Your Own Agents
    Plain
    Available
    Sierra
    Not available
  • API
    Plain
    Available
    Sierra
    Limited
  • Help Center and Knowledge Base
    Plain
    Available
    Sierra
    Not available
  • Agent Studio
    Plain
    Not available
    Sierra
    Available
  • Ghostwriter
    Plain
    Not available
    Sierra
    Available
  • Voice agents
    Plain
    Not available
    Sierra
    Available
  • Multi-channel deployment
    Plain
    Not available
    Sierra
    Available
  • Horizon
    Plain
    Limited
    Sierra
    Available
  • Context Engine
    Plain
    Not available
    Sierra
    Available
  • Insights and Explorer
    Plain
    Not available
    Sierra
    Available
  • Experiments
    Plain
    Not available
    Sierra
    Available
  • Knowledge management
    Plain
    Not available
    Sierra
    Available
  • Trust and reliability
    Plain
    Not available
    Sierra
    Available

Limited means partial support or a paid add-on.

Pricing

Plans as listed by each vendor. Check their sites for current prices.

  • Pricing model
    Plain
    Free trial
    Sierra
    Paid
  • Free plan
    Plain
    No
    Sierra
    No
  • Starting price
    Plain
    $45
    Sierra
    Custom
  • Plans
    Plain
    3 plans
    Sierra
    1 plan

Plain plans

  • Foundation

    Most popular

    $45/user/mo

    Small teams getting started with support

    • 1,000 credits/month
    • Sidekick
    • Ari
    • AI workflows
    • Slack
    • email and in-app channels
    • Linear and Jira integrations
    • Help Center
    • Knowledge Base

  • Horizon

    $99/user/mo

    Growing teams with more complex workflows

    • 2,500 credits/month
    • Microsoft Teams
    • SLAs and business hours
    • escalation paths
    • CRM integrations
    • reporting themes
    • AI suggested responses

  • Frontier

    Custom/custom

    Larger organizations needing governance and control

    • Custom credits
    • multiple workspaces
    • custom contracting
    • advanced security
    • SSO and SCIM
    • HIPAA
    • white glove onboarding
    • dedicated customer success manager

Sierra plans

  • Enterprise

    Most popular

    Custom/custom

    Outcome-based pricing quoted through Sierra sales

    • Agent Studio
    • Ghostwriter
    • Insights
    • Multiple channels
    • Context Engine

Our ratings

Scored out of 10 by the Finder Atlas editorial team. Last reviewed November 2026.

Plain
7.9overall
Sierra
7.6overall

Plain leads in 3 categories and Sierra in 2.

  • Ease of Use

    Plain leads by 0.5
    Plain
    8.0
    Sierra
    7.5

  • Feature Depth

    Sierra leads by 0.3
    Plain
    8.2
    Sierra
    8.5

  • Value for Money

    Plain leads by 0.3
    Plain
    7.3
    Sierra
    7.0

  • Performance & Speed

    Sierra leads by 0.2
    Plain
    7.8
    Sierra
    8.0

  • Documentation & Support

    Plain leads by 1.0
    Plain
    8.0
    Sierra
    7.0

Scores weigh documented features, plan value, platform coverage, integrations and user feedback. A missing score means we have not rated that area yet.

Pros and cons

Plain

Pros

  • Built around B2B support, with Slack, Teams and Discord channels alongside email and chat.
  • Ari and Sidekick AI agents are included from the entry plan.
  • API-first design allows custom workflows and embedding.
  • 7-day trial without a credit card, plus a 50% startup discount.
  • Enterprise options include SSO, SCIM and HIPAA on the Frontier plan.

Cons

  • No permanently free plan; paid plans start at $45 per user per month.
  • AI usage is metered in credits (1,000 per month on Foundation), which makes costs harder to predict.
  • Microsoft Teams and CRM integrations require the $99 Horizon plan.
  • No iOS or Android app was found.

Sierra

Pros

  • Outcome-based pricing ties cost to results rather than seats or tokens.
  • Covers voice, chat, SMS, WhatsApp, email and ChatGPT from one agent build.
  • Ghostwriter can create agents from existing SOPs, transcripts or audio interviews.
  • Large enterprise customer base named on the homepage, including Uber, Vanguard and Hyatt.
  • Broad compliance list, including SOC 2, ISO 42001, HIPAA and FedRAMP.
  • Built-in analytics, monitors and experiments for tuning agent behavior.

Cons

  • No published pricing and no self-serve signup or free trial found.
  • Aimed at enterprises; small businesses are not the evident target.
  • Outcome-based billing can make monthly cost harder to forecast.
  • Public documentation for developers (API or SDK) was not found on the official site.

Platforms

  • Web
    Plain
    Supported
    Sierra
    Supported
  • Windows
    Plain
    Not supported
    Sierra
    Not supported
  • macOS
    Plain
    Not supported
    Sierra
    Not supported
  • iOS
    Plain
    Not supported
    Sierra
    Not supported
  • Android
    Plain
    Not supported
    Sierra
    Not supported
  • API
    Plain
    Supported
    Sierra
    Not supported
  • Browser Extension
    Plain
    Not supported
    Sierra
    Not supported

Integrations

Plain

6 integrations
  • Slack
  • Microsoft Teams
  • Discord
  • Linear
  • Jira
  • PagerDuty

Sierra

9 integrations
  • Snowflake
  • Databricks
  • Redis
  • AWS
  • Google Cloud
  • Slack
  • Microsoft Teams
  • WhatsApp
  • ChatGPT

Company

  • Company
    Plain
    Plain
    Sierra
    Sierra Technologies, Inc.
  • Founded
    Plain
    2020
    Sierra
    2023
  • Headquarters
    Plain
    London, United Kingdom
    Sierra
    San Francisco, USA
  • Listing
    Plain
    Claimed
    Sierra
    Claimed

Frequently asked questions

Is Plain better than Sierra?

It depends on your workflow. Plain is built for Teams that support business customers through shared Slack or Teams channels and want AI triage, routing and an API-first setup. Sierra is built for large companies automating high-volume customer conversations across voice and digital channels with outcome-based pricing.

What are the key feature differences between Plain and Sierra?

Plain: AI-powered support platform for B2B teams, unifying Slack, email and chat in one workspace. Sierra: Enterprise AI agents that handle customer conversations across voice, chat and messaging, priced by outcome.

Does Plain or Sierra have a free plan?

Neither has a free plan. Both Plain and Sierra are paid products.

Which is cheaper, Plain or Sierra?

Plain starts at $45 and Sierra starts at Custom. See the pricing table above for what each tier includes.