“Claude or Copilot?” is a fair question for a firm to ask. “For what?” is a more useful one. Copilot is strongest on work that already lives in Microsoft 365: email, Teams meetings, Excel files in SharePoint. Claude is strongest on long documents and drafting, especially when a matter’s materials sit together in a project.
Neither tool removes the two jobs that matter most. Someone still has to check every citation, and someone has to clean up who can see what before either assistant goes near matter files. Our broader Claude vs Copilot comparison covers security and licensing. This guide is about daily tasks.
A note on names: Microsoft has renamed Microsoft 365 Copilot to Microsoft Copilot, and some licenses and screens still use the old name. Product details below were checked against Microsoft and Anthropic documentation as of October 2026.
The short answer: Claude or Copilot for legal work
If the task starts in an inbox, a Teams meeting or a spreadsheet, start with Copilot. It works inside the apps and grounds its answers in Microsoft Graph content the user can already view.
If the task starts with a stack of documents you want to read closely, compare or draft from, start with Claude. Projects keep a matter’s reference files and instructions together across chats.
If your firm ends up licensing both, that’s fine, as long as the rules and the permissions cleanup are done once and apply to both.
Task-by-task: which tool, which guardrail
| Task | Better starting point | Why | Guardrail |
|---|---|---|---|
| Matter intake | Copilot | Intake lives in email, forms and Teams threads already in Microsoft 365 | Conflicts check stays in your conflicts system; AI summarizes, people decide |
| First drafts of letters, memos and clauses | Claude | Strong long-form drafting; a project can hold templates, style rules and the matter’s background | Lawyer review of every draft; no client facts in any tool outside the approved one |
| Deposition summaries and long documents | Claude | Projects keep long material together for close reading and comparison | Spot-check summaries against the transcript; page and line cites verified by a person |
| Email triage | Copilot | Works in Outlook on the user’s own mail | Copilot reaches what the user can open, so delegate and shared mailbox access matter |
| Excel billing analysis | Copilot | Works inside the workbook with tables, formulas and PivotTables | File must live in OneDrive or SharePoint with AutoSave on; check totals before anything reaches a client |
| Research memos | Either, with care | Both draft well; neither replaces a citator | Every case pulled and read before it appears in work product |
| Teams meeting recaps | Copilot | Organizer controls Copilot per meeting; recaps tie to the meeting record | Transcription and Copilot settings chosen before client calls start |
The table is a starting point. A firm with most matter files in a separate document management system will see different results than one that works mainly in SharePoint, which brings us to the first real constraint.
Where Copilot fits, and where it stops
Copilot’s advantage is location. Microsoft’s Copilot data, privacy and security documentation says it surfaces only organizational data to which each user has at least view permissions. It combines that with the user’s working context: the meeting they’re in, the thread they’re reading. For email triage and meeting follow-up, that’s hard to beat.
That same design is the risk. If a SharePoint site with privileged material is shared with everyone in the firm, Copilot can surface it to everyone in the firm. Our post on whether Microsoft Copilot is safe for law firms goes into the permission work.
Three practical limits are worth knowing before you promise anyone results:
- Your DMS may be outside its reach. Copilot grounds in Microsoft Graph content. Microsoft says Copilot can reference third-party tools and services through Microsoft Graph connectors or agents, so files in a separate document management system are in scope only if one of those is set up.
- Excel has file requirements. Copilot in Excel works on .xlsx, .xlsb and .xlsm files saved to OneDrive or SharePoint with AutoSave on, with data formatted as a table or a supported range. On SharePoint sites that require check-out for editing, Microsoft says Copilot in desktop Excel won’t work; Excel for the web still can.
- Client-hosted meetings are out. Microsoft says Copilot won’t work in meetings hosted outside the participant’s organization. If a client sends the invite, plan on your own notes.
On meetings, the organizer chooses whether Copilot runs during and after the meeting (transcription required), only during it, or not at all. Setting it to off also disables recording and transcription. For a call that touches strategy, that choice deserves a moment before the meeting starts.
Where Claude fits, and what to set up first
Claude is the better fit for close reading and drafting. Projects give each matter or practice group a workspace with its own files and instructions, separate from other chats. On paid plans, when project knowledge gets close to the context limit, Claude switches to searching the project’s files instead of loading everything at once. That suits a deposition set or a contract stack.
Claude can also reach Microsoft 365 through Anthropic’s Microsoft 365 connector, which searches SharePoint, OneDrive, Outlook and Teams with the user’s existing permissions. Setup matters here:
- On Team and Enterprise plans, a Claude organization Owner has to enable the connector, and a Microsoft Entra Global Administrator grants one-time tenant consent.
- Write tools (sending email, creating files, posting to Teams) are off unless an admin enables them.
- You can’t scope the connector to specific SharePoint sites. Anthropic’s documentation says Sites.Selected isn’t supported, so it searches everything the user can reach.
That last point is the one I’d flag to any managing partner. A SharePoint permissions problem stays in place when you license Claude, and Claude inherits it the same way Copilot does.
Plan choice matters too. Claude Team and Claude Enterprise both include no model training on your content by default. Enterprise adds SCIM provisioning, audit logs and custom data retention controls. If your clients send security questionnaires, check which of those controls they ask about. Our Claude Team vs Enterprise breakdown covers that decision.
Citations, hallucinations and privilege
Every task in the table has the same failure mode: confident output that’s wrong. Microsoft’s own documentation says Copilot responses aren’t guaranteed to be 100% factual and should be reviewed before they go to anyone else. The same caution applies to Claude and every other assistant. One example is Mata v. Avianca, Inc. (S.D.N.Y. 2023). The court sanctioned two lawyers and their firm under Rule 11 after they submitted opinions that ChatGPT had made up, then kept standing by them.
For lawyers, the reference point is ABA Formal Opinion 512, issued July 29, 2024. It ties generative AI use to Model Rules 1.1 (competence), 1.6 (confidentiality), 1.4 (communication) and 1.5 (fees). On fees, the ABA’s summary says a lawyer may bill time spent entering information and reviewing an AI draft, but generally can’t bill the client for learning the tool. We also cover what 512 asks of your Claude and Copilot setup.
In practice, that turns into a few firm rules:
- No case, statute or quote goes into work product until a person has pulled and read the source.
- Client information goes only into tools the firm approved for that matter type.
- Engagement letters and client conversations reflect how the firm uses AI, where your ethics counsel says they should.
Privilege questions turn on facts and jurisdiction, and using an approved enterprise tool doesn’t settle them by itself. This isn’t legal advice, and your ethics counsel should weigh in on your firm’s approach.
If you’d like a quick read on whether your permissions are ready for either tool, the free AI Readiness Snapshot covers that.
Licensing both without doubling the risk
Two assistants can mean two sets of risk, or one set of controls applied twice. The difference is whether you do the groundwork once:
- One permissions cleanup. Both tools see what each user can see. Fix overshared sites and broken inheritance before either rollout.
- One acceptable use policy. Same data rules, same verification rule, regardless of which assistant someone opens.
- One approval owner. Someone decides which connectors are on, which write tools are enabled and which plan each group gets.
- Clear lanes. Tell people which tool to use for which task. The table above is a reasonable first draft.
For the platform-level comparison of the two products, see Claude Enterprise vs Microsoft 365 Copilot.
Quick answers
Is Claude or Copilot better for legal drafting?
For long-form drafting from a set of documents, Claude is usually the better starting point, because projects keep templates and matter background together. For quick drafts inside Word or Outlook that draw on email and files already in Microsoft 365, Copilot is more convenient. Either way, a lawyer reviews the draft before it goes anywhere.
Can Copilot summarize depositions?
Yes, Copilot can summarize a transcript stored in Microsoft 365, and it works well for a first pass. For very long transcripts or comparisons across several depositions, a project-based tool like Claude can be easier to work with, because the files stay together. In both cases, verify page and line references against the transcript before relying on them.
Do lawyers need to verify AI citations?
Yes. ABA Formal Opinion 512 connects AI use to the duty of competence, and Microsoft’s documentation says Copilot output isn’t guaranteed to be factual. Treat every case name, quote and pin cite as unverified until a person has pulled the source. Courts have sanctioned filings that cited cases that don’t exist.
Can a firm license both Claude and Copilot?
Yes. The key is doing the groundwork once, starting with permissions and the acceptable use policy. Both tools respect existing Microsoft 365 permissions when they reach into Microsoft 365, so a permissions problem affects both. Assign each tool to the tasks it handles best, and tell people which is which.
Where to start
Pick the two or three tasks your lawyers do most and match them to the table. Then check the guardrail column against what’s configured today. That gap is where the real project starts.
If you want a second opinion on readiness, the AI Readiness Snapshot is free: a 60-minute working session, written findings and a 30-minute review. It covers permissions and data access whether you’re planning Claude, Copilot or both. For the bigger comparison, start with our Claude vs Copilot guide.
