Updated September 2025. This practical, no-fluff comparison is for U.S. lawyers, in-house counsel, and legal ops teams evaluating the two market leaders in AI-powered legal research.
Bottom Line
-
Choose Westlaw Precision AI if your day-to-day relies on Westlaw’s ecosystem (Key Number System, KeyCite) and you want structured, explainable AI research that points back to primary law and editorial analysis.
-
Choose Lexis+ AI if you want conversational research paired with Shepard’s signal checks, drafting inside Microsoft Word (via add-ins), and tighter connections to your DMS (iManage, NetDocuments, SharePoint) to leverage prior work product.
-
Either way: treat outputs as drafts, verify every citation, and lock your scope to the correct jurisdiction and court rules.
At-a-glance: Feature Comparison
| Capability | Westlaw Precision AI | Lexis+ AI |
|---|---|---|
| Core research experience | Guided AI research inside Westlaw; answers link back to primary law and editorial enhancements. | Conversational research; answers include linked authorities and Shepard’s treatment for validation. |
| Citation validation | KeyCite with depth of treatment, negative treatment flags, and related-authority discovery. | Shepard’s signals integrated into responses to help spot negative or limited treatment. |
| Drafting | Drafting support via Westlaw ecosystem and Practical Law forms/checklists. | Word-native drafting and review via add-ins (clause suggestions, cite insertion, formatting checks). |
| DMS / knowledge grounding | Works best alongside Practical Law know-how and saved research folders. | Common connectors (iManage, NetDocuments, SharePoint) to reference prior filings and templates. |
| Litigation tools | Strong for briefs, motion practice, and appellate research; deep editorial analysis. | Strong for litigation and regulatory work with Shepard’s and analytics in higher tiers. |
| Transactional support | Practical Law for deal checklists, model clauses, and market practice notes. | Word-based drafting flows and clause extraction; integrates with playbooks in many setups. |
| Security & privacy posture | Enterprise controls, contractual data-use restrictions, org-scoped history. | Enterprise controls, contractual data-use restrictions, org-scoped history. |
| Pricing | Quote-based; bundles vary by content sets, seats, and add-ons. | Quote-based; bundles vary by content sets, seats, and add-ons. |
| Who it’s best for | Litigators/appellate specialists and anyone already “thinking in Westlaw” (KeyCite/Key Numbers). | In-house teams and firms standardizing Word-native drafting with Shepard’s validation and DMS grounding. |
What Actually Feels Different in Daily Use
1) Research flow and answer shape
-
Westlaw Precision AI tends to present answers like a structured memo: identifies the issue, states the rule, surfaces controlling authorities, and links into Westlaw’s editorial layers.
-
Lexis+ AI feels more like chat-assisted research: you iterate quickly, then jump into full-text statutes/cases with Shepard’s treatments visible as you validate.
2) Citation trust and verification
-
KeyCite vs. Shepard’s remains the practical fork. Establish a house rule: every AI-suggested citation must be opened, read, and verified before use.
3) Drafting beyond search
-
Westlaw side: Practical Law templates, checklists, and drafting notes help first drafts and issue-spotting for transactional teams.
-
Lexis side: The Microsoft Word add-ins reduce context switching—suggest language, insert cites, run a light review without leaving your draft.
4) Using your own knowledge base
-
DMS grounding (often with Lexis+ AI) can reference iManage/NetDocuments/SharePoint so your prior briefs and templates inform suggestions.
-
Westlaw users often pair AI research with saved research folders and Practical Law to keep style and authority consistent.
Pros & Cons
Westlaw Precision AI
Pros
-
Deep editorial layers (Key Number System) aid issue-spotting and related-authority discovery
-
Clear ties to Practical Law for checklists and model language
-
Strong fit for litigation and appellate workflows
Cons
-
Quote-based pricing can feel opaque; bundles matter
-
Best value when your team already lives in Westlaw
-
Drafting often means moving between tools (research → template → Word)
Lexis+ AI
Pros
-
Conversational research with Shepard’s signals helps early validation
-
Word-native drafting flows reduce context-switching
-
Common connectors to iManage/NetDocuments/SharePoint support reuse of prior work product
Cons
-
Quote-based pricing; features vary by tier
-
Research can feel “chat-first” if you prefer memo-style answers
-
DMS setup/permissions require coordination with IT/InfoSec
Buyer’s Checklist
-
Run identical prompts in both tools for one current matter (jurisdiction-specific).
-
Measure four things: answer time, number of controlling authorities surfaced, cleanup time after verification, and final quality of your memo/draft.
-
Stress-test hallucinations: ask for niche issues, conflicting authorities, and “split” jurisdictions. Verify every cite.
-
Drafting trial: prepare a short brief section or contract clause in each tool’s preferred workflow (Practical Law vs Word add-in). Time the full loop.
-
DMS connection (if applicable): enable read-only access to a small, sanitized folder. Check whether suggestions match your house style.
-
InfoSec packet: lock down data-use, retention, and user-history settings in writing.
-
Pricing: request 2–3 configurations (solo/small team/firmwide) with transparent content bundles. Negotiate multi-year terms with review checkpoints.
Who Should Choose Which?
-
Choose Westlaw Precision AI if you’re a litigator or appellate lawyer who lives in KeyCite and appreciates structured, memo-like answers plus tight connections to Practical Law.
-
Choose Lexis+ AI if you want Word-native drafting with Shepard’s-checked citations and plan to ground the system on your DMS to reuse proven language.
-
Solo & small firms: trial both. The “better” tool is the one that yields fewer post-AI edits for the exact matters you handle.
Common Pitfalls (and How to Avoid Them)
-
Copy-pasting AI answers. Always open and read each authority; courts notice miscites.
-
Ignoring jurisdiction. Pin your research to the right state/federal scope at the start.
-
Unclear prompts. Provide facts, posture, and the relief sought. Ask for controlling authorities and majority/minority views.
-
Skipping playbooks. Capture what works (prompt style, filters, validation steps) in a short internal playbook.
Quick Start Prompts (Steal These)
-
“You are my research assistant. Jurisdiction: [State/Federal]. Issue: [X]. Provide a rule statement, 3–5 controlling authorities with parentheticals, and a short analysis. List contrary authority if any.”
-
“Draft a first-cut clause for [topic] consistent with [our] prior template language. Flag risks and alternative positions.”
-
“Generate a validation checklist for the citations above, including quotes to verify and negative treatment to check.”
FAQ
Is either tool “hallucination-free”?
No. They reduce risk by linking to authorities, but you must open and verify each citation before relying on it.
Which is cheaper?
Both are quote-based. Your price depends on seats, jurisdictions, and add-ons. Always request multiple configurations and negotiate.
Can I trust AI to write my brief or agreement?
Treat outputs as drafts. Use them to accelerate first cuts, then apply attorney review, cite checking, and style conformity.
What if my firm uses a DMS?
Connectors can help reuse prior work product. Start with a small, sanitized folder, confirm access controls, and evaluate whether suggestions match your style.
Both platforms can meaningfully speed up legal work—but they shine in different lanes. Choose Westlaw Precision AI if your practice already runs on KeyCite/Key Numbers and you value structured, memo-style answers paired with Practical Law. Choose Lexis+ AI if you want Word-native drafting, Shepard’s-checked citations, and tighter DMS grounding to reuse firm work product. Either way, treat outputs as drafts and verify every citation. The smartest move now: run an apples-to-apples pilot on a live matter, measure time saved and post-AI edit load, and then negotiate multi-year pricing that fits your content bundles.
