Legal research is where AI has the highest stakes and the highest potential in law. Get it right, and you save hours of associate time. Get it wrong, and you end up like Steven Schwartz — sanctioned for submitting fabricated case citations generated by ChatGPT. The difference between general AI and legal-specific AI research tools is the difference between a helpful shortcut and a career-ending mistake.

I talked to attorneys using all three platforms to compare them honestly.

Quick Comparison

Feature	Westlaw AI (AI-Assisted Research)	Lexis+ AI	CoCounsel (by Thomson Reuters)
Price	Included with Westlaw subscription	Included with Lexis+	Separate subscription (~$100-200/user/mo)
AI model	Proprietary + GPT-4	Proprietary + GPT-4	GPT-4 with legal training
Citation verification	✅ Verified against Westlaw database	✅ Verified against Lexis database	✅ Verified
Hallucination risk	Low	Low	Low
Natural language queries	✅ Yes	✅ Yes	✅ Yes
Document analysis	✅ Good	✅ Good	✅ Best
Memo drafting	⚠️ Basic	⚠️ Basic	✅ Strong
Integration	Westlaw ecosystem	Lexis ecosystem	Standalone + Westlaw

Westlaw AI-Assisted Research

What It Does

Westlaw’s AI features let you search using natural language instead of Boolean queries. Ask “What is the standard for summary judgment in employment discrimination cases in the Ninth Circuit?” and it returns relevant cases with AI-generated summaries. It also suggests related searches and highlights the most relevant passages.

Strengths

The biggest advantage: every citation is verified against Westlaw’s database. If the AI references a case, that case exists and says what the AI claims it says. This is the fundamental difference between Westlaw AI and ChatGPT — and it’s worth everything.

The integration with KeyCite means you can instantly check if a cited case is still good law. The AI summaries are concise and generally accurate, saving the time of reading full opinions to determine relevance.

Weaknesses

The AI features feel bolted onto the existing Westlaw interface rather than built from the ground up. The natural language search is good but not transformative — experienced Westlaw users often get better results with traditional Boolean searches for complex queries. And the AI can’t draft memos or analyze uploaded documents — it’s a research tool, not a drafting tool.

Best For

Firms already on Westlaw who want AI-enhanced research without changing platforms. The AI features are included in the subscription, so there’s no additional cost.

Lexis+ AI

What It Does

Similar to Westlaw’s AI: natural language search, AI-generated case summaries, and citation verification against the LexisNexis database. Lexis+ AI also includes conversational search — you can ask follow-up questions to refine results, similar to chatting with a research assistant.

Strengths

The conversational interface is more intuitive than Westlaw’s. You can ask “Now narrow that to cases from the last 5 years” or “What about in the Second Circuit instead?” without starting a new search. For attorneys who think in questions rather than search terms, this feels more natural.

The Practical Guidance integration is useful — it connects AI research results to practice notes, checklists, and forms, giving you both the law and the practical application.

Weaknesses

The AI summaries occasionally oversimplify complex holdings. I heard from a litigator who found that Lexis+ AI summarized a case as supporting his position when the actual holding was more nuanced and partially unfavorable. The summary wasn’t wrong — it was incomplete. Always read the actual opinion for cases you plan to cite.

Like Westlaw, the AI features enhance research but don’t extend to drafting or document analysis.

Best For

Firms already on LexisNexis who want a more conversational research experience. Particularly good for attorneys who prefer asking questions over constructing searches.

CoCounsel

What It Does

CoCounsel goes beyond research into document analysis and drafting. Upload a contract and ask it to identify risky clauses. Paste a set of facts and ask it to find relevant case law. Give it a legal question and it drafts a research memo with verified citations. It’s the most ambitious of the three — trying to be a junior associate, not just a search engine.

Strengths

Document analysis is CoCounsel’s standout feature. Upload a 50-page contract and ask “What are the indemnification obligations?” or “Flag any non-standard termination provisions.” It reads the document and provides specific, cited answers. For transactional attorneys reviewing stacks of contracts, this is genuinely transformative.

The memo drafting is solid — not partner-ready, but a strong first draft that saves hours of associate time. Citations are verified, the analysis is structured, and the output follows standard legal memo format.

Weaknesses

The price. At $100-200 per user per month on top of your existing Westlaw or Lexis subscription, it’s a significant investment. For solo practitioners and small firms, the math is harder to justify than for BigLaw.

The research capabilities, while good, aren’t dramatically better than Westlaw or Lexis AI for straightforward legal research. CoCounsel’s advantage is in the document analysis and drafting features — if you don’t need those, you’re overpaying.

Best For

Mid-size to large firms doing high-volume contract review or complex litigation with extensive document analysis needs. The ROI is clearest when it replaces hours of junior associate document review time.

The Verdict

If you…	Use this
Already have Westlaw	Use Westlaw’s built-in AI (free with subscription)
Already have LexisNexis	Use Lexis+ AI (free with subscription)
Need document analysis + drafting	Add CoCounsel ($100-200/mo)
Are a solo/small firm on a budget	Stick with your existing platform’s AI
Do high-volume contract review	CoCounsel pays for itself

The honest answer for most attorneys: use whichever platform you already subscribe to. Westlaw AI and Lexis+ AI are comparable in quality, and switching platforms for marginal AI improvements doesn’t make sense when you factor in the learning curve and workflow disruption.

Add CoCounsel only if document analysis and memo drafting would save you measurable hours each week. For a firm billing associates at $300+/hour, replacing 10 hours of associate time per month with a $200 subscription is an obvious win. For a solo practitioner, the math is tighter.

And regardless of which tool you use: verify every citation. Read every case you plan to cite. AI legal research is a starting point, never a finished product.

Related reading: CoCounsel Review — AI Legal Research Worth the Price? · AI for Due Diligence — Speed Up Document Review Without Missing Red Flags · AI for Small Law Firms — Best Tools Under $50/Month

🛠️ Need to draft a legal document? Try our Legal Document Drafter — NDAs, contracts, demand letters. Free.