Here’s a practical comparison framework you can use to evaluate Microsoft Search, Glean, Elastic, or a custom build for internal docs and messages.

1) Permissions and access control

This is the most important factor for enterprise search.

Compare:

• Source-of-truth enforcement
  • Does the product respect native permissions from SharePoint, OneDrive, Google Drive, Slack, Teams, Jira, Confluence, etc.?
  • Does it re-check permissions at query time, or only at index time?
• Granularity
  • File-level only, or also folder, workspace, channel, thread, page, row, and record-level permissions?
• Dynamic ACL sync
  • How quickly does it update when access changes?
  • Can revoked access disappear immediately?
• Identity integration
  • Supports Okta, Entra ID/Azure AD, Google Workspace, SCIM?
  • Can it handle group nesting, external users, guests, contractors?
• Auditability
  • Can admins see why a result was shown or hidden?
  • Are access decisions logged for compliance?

What to watch for

• If permissions are not inherited perfectly from source systems, search can leak sensitive content.
• For custom builds, ACL handling is often the hardest part.

2) Citations and answer trustworthiness

If you want AI-assisted search or summarization, citations matter a lot.

Compare:

• Source citations
  • Does it show exact document/message links?
  • Does it cite paragraphs, snippets, timestamps, or message threads?
• Answer grounding
  • Are answers generated only from retrieved documents, or can the model hallucinate?
  • Can it quote multiple sources?
• Confidence and traceability
  • Does it show why a result was returned?
  • Can users open the exact source context?
• Freshness
  • How quickly are citations updated after source changes?
• Citation quality controls
  • Can admins require citations for all AI answers?
  • Can they disable generative answers if risk is too high?

What to watch for

• A product can be good at search but weak at explainability.
• If users can’t verify answers quickly, trust drops fast.

3) Connectors and ingestion

This is where coverage and maintenance live.

Compare:

• Native connectors
  • Microsoft 365, Google Workspace, Slack, Teams, SharePoint, OneDrive, Gmail, Drive, Jira, Confluence, Notion, Box, Dropbox, Salesforce, Zendesk, etc.
• Message and document support
  • Does it support chat messages, attachments, threads, comments, and version history?
• Metadata preservation
  • Title, author, timestamps, channel, workspace, labels, ACLs, custom fields
• Incremental sync
  • Near-real-time vs batch
• API and custom sources
  • Can you build custom connectors easily?
• Normalization
  • Does it dedupe, extract text, OCR PDFs/images, and parse attachments?

What to watch for

• Connector depth matters more than count.
• A “connector” that only imports titles and text but loses ACLs or metadata is not enough for enterprise use.

4) Admin controls and governance

Admins need control over safety, relevance, and scope.

Compare:

• Index scope
  • Which org units, workspaces, sites, or channels can be included/excluded?
• Permission policy controls
  • Can admins enforce strict ACL sync and block public indexing?
• Content controls
  • Exclude sensitive locations, legal holds, HR repositories, finance folders, or private channels
• AI controls
  • Toggle generative answers on/off
  • Restrict which sources AI can use
  • Require citations
  • Control prompt logging and retention
• Relevance tuning
  • Boost authoritative sources, recent content, people results, or official docs
• User experience controls
  • Branding, query suggestions, synonyms, facets, result ranking rules
• Monitoring
  • Usage analytics, failed connectors, stale indexes, access denials, zero-result queries
• Compliance
  • Data retention, eDiscovery, audit logs, DLP support, regional data residency

What to watch for

• Admins often need “policy by source” rather than global settings.
• Search can become unsafe if admins can’t exclude sensitive repositories.

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How the options usually differ

Microsoft Search

Best if:

• You’re deeply on Microsoft 365 / Entra / SharePoint / Teams
• You want strong native permissions and relatively easy deployment
• You care about Microsoft ecosystem integration more than broad cross-app search

Tradeoffs:

• Best inside the Microsoft stack, less universal outside it
• Custom relevance and non-Microsoft connector depth may be limited compared with specialized products

Glean

Best if:

• You want broad enterprise connectors and a polished cross-app experience
• You care about fast time-to-value and strong AI search/answer UX
• You want robust enterprise permissions handling across many SaaS tools

Tradeoffs:

• Less control than building yourself
• Cost can be significant at scale
• You still need governance reviews for data exposure, AI usage, and connector scope

Elastic

Best if:

• You want a flexible search platform and have engineering resources
• You need custom ranking, custom pipelines, or specific data sources
• You may want to extend into logs/observability/search applications

Tradeoffs:

• You must build and maintain connectors, permission sync, ranking, AI layer, and admin UX
• Strong platform, but not an out-of-the-box enterprise search product unless you assemble one

Build it yourself

Best if:

• You have highly unique requirements, strict compliance constraints, or proprietary content types
• You need exact control over permissions, ranking, residency, audit, and UI

Tradeoffs:

• Highest engineering and maintenance burden
• ACL sync, connector maintenance, citations, and admin tooling are all non-trivial
• Time to value is usually much slower

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Suggested evaluation checklist

Use these questions in demos:

Permissions

• How do you enforce source permissions?
• How fast do permission changes propagate?
• How are guest/external users handled?
• Can you show an audit trail for why a result was accessible?

Citations

• Do AI answers include source-level citations?
• Can I click to the exact message/doc/paragraph?
• Can admins require citations for every answer?
• How do you prevent hallucinations?

Connectors

• Which connectors are native vs partner vs custom?
• Do you support messages, attachments, threads, versions, comments?
• Do ACLs and metadata survive ingestion?
• How often do you sync?

Admin controls

• Can we exclude sensitive repositories and channels?
• Can we restrict AI to approved sources?
• Can we monitor stale connectors, failed syncs, and usage?
• Can we adjust ranking and synonyms without engineering?

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A simple decision rule

• Choose Microsoft Search if most content is already in Microsoft 365 and you want lowest operational complexity.
• Choose Glean if you need the best cross-app enterprise search experience quickly.
• Choose Elastic if you have a strong engineering team and need high customization.
• Build only if off-the-shelf tools can’t satisfy your permission, compliance, or UX requirements.

If you want, I can turn this into a scored vendor evaluation matrix with columns for Microsoft Search, Glean, Elastic, and build-vs-buy, ready to use in procurement.