best ai for legal document review

Analysis: how 3 AI models compare

Agreement: 72%  •  Divergence: 35%

All three AIs identify Harvey, CoCounsel, Spellbook, Luminance, Kira, and Relativity as top legal AI tools by category.

Where the models agree

• **Harvey AI** is consistently identified as the top enterprise-grade legal AI platform, best suited for large law firms with complex needs and premium pricing.
• **CoCounsel** (formerly Casetext, now Thomson Reuters) is recognized for its strong integration with Westlaw/Practical Law and best value for firms already in that ecosystem.
• **Spellbook** is agreed upon as ideal for small to mid-size firms, working inside Microsoft Word, offering affordable contract drafting/review.
• **Luminance** is recommended for M&A due diligence and large-scale contract analysis using pattern-recognition technology.
• **Kira Systems** (now part of Litera) is noted for precise clause extraction and strong track record in due diligence/M&A.
• **Relativity** (RelativityOne/aiR) is identified as the industry standard for eDiscovery and litigation at massive scale.
• **General-purpose LLMs** (ChatGPT, Claude, Gemini) are considered useful for low-risk tasks like summarization and drafting but carry hallucination risks and require human verification.
• **Hallucination risk** is a universally cited concern—AI can fabricate facts or citations, requiring verification.

Where they differ

• Specific law firms using Harvey AI: **Claude** specifically names Allen & Overy and PwC as Harvey AI users. **DeepSeek** only generally references 'many AmLaw 100 firms' without naming specific firms. **ChatGPT** also vaguely references 'major firms and institutions' without naming specific ones.
• Breadth of tool coverage: **ChatGPT** includes significantly more tools not mentioned by the others, such as **LawGeex**, **Lexis+ AI**, **eBrevia**, **LegalOn**, **Juro AI**, **Robin AI**, **Reveal**, **Casepoint**, **Icertis**, **Sirion**, **Agiloft**, and **DraftWise**-style CLM platforms with generative AI. **Claude** uniquely mentions **LawGeex**, **Ironclad AI**, and **DraftWise** as distinct entries not covered by DeepSeek. **DeepSeek** does not mention LawGeex, Lexis+ AI, or eBrevia at all.
• Categorization approach for tools: **DeepSeek** organizes tools into a flat list of 8 major contenders with individual strengths/weaknesses. **ChatGPT** uses a more granular categorization splitting eDiscovery, contract review, and generative AI-native tools into separate subsections with more tools per category. **Claude** uses a simpler two-tier split (enterprise-grade vs. mid-market) with fewer total tools discussed.
• Recommendation for litigation teams: **DeepSeek** recommends Relativity aiR, Everlaw, or DISCO for litigation teams. **Claude** recommends Relativity and CoCounsel for e-discovery/litigation (notably including CoCounsel here, which the others frame primarily as a research/contract tool). **ChatGPT** recommends Relativity, Reveal, Everlaw, DISCO, or Logikcull/Casepoint for smaller matters, introducing additional platforms (Reveal, Casepoint) not mentioned by the other two.
• Treatment of Microsoft/Azure tools: **ChatGPT** uniquely discusses **Microsoft Copilot (M365)** and **Azure OpenAI** as viable options for legal document review, especially for organizations already on Microsoft 365. Neither **DeepSeek** nor **Claude** mention Microsoft Copilot or Azure OpenAI as options at all.
• Level of implementation guidance provided: **ChatGPT** provides an extensive implementation strategy section (pilot programs, guardrails, governance policies, 30-60 day pilot plans) that goes far beyond what **DeepSeek** and **Claude** offer, which stick to selection criteria and brief caveats without detailed rollout strategies.