ChatGPT vs Claude for Lawyers: Which One, for What, in 2026

On 16 June 2026 Davide DeMango gave GPT-4o, Gemini 1.5 Pro and Claude Sonnet 3.5 the same prompt: a services agreement for a freelance web designer, drafted on the freelancer’s side. GPT-4o wrote a “broad and bilateral” indemnity that left the freelancer exposed. Gemini was vague, with no liability cap and no third-party IP carve-out. Only Claude produced “a mutual indemnification structure with a carve-out for third-party IP infringement claims” (DeMango’s write-up).

Those were 2024-era models, and one test proves little. But it is the right kind of evidence for the ChatGPT vs Claude for lawyers question: the same task in both tools, read by a lawyer. The honest verdict is that the brand matters less than the tier you are on, the task you give it and whether you read what comes back. Where the two differ, the differences are specific, and for a European firm some are decisive.

ChatGPT vs Claude for lawyers: the short answer by task

If you read one section, read the confidentiality tiers: that is where lawyers get hurt.

Drafting: the three-model indemnity test

The DeMango test is about defaults. Nobody told the models which side to protect beyond “freelancer-favourable”; GPT-4o defaulted to a symmetry that hurt its client, Gemini to vagueness, Claude to a structure a practitioner would recognise. The lesson is not “use Claude” but that a model’s defaults are not your playbook: specify who indemnifies whom, the carve-outs and the cap.

On the benchmarks the families have converged. Harvey’s BigLaw Bench reported Claude Opus 4.6 at 90.2% in February 2026 and Opus 4.7 at 90.9% in May; GPT-5 scored 89.22% in August 2025. Vendor-designed and dated differently (how to read legal AI benchmarks), they say both are good enough that the prompt decides. They also want different prompts: OpenAI says “think step by step” is unnecessary for its o-series reasoning models, Anthropic says “double-check your answer” lines “cause over-verification” on Opus 5 (prompting reasoning models for legal work).

Draft three versions of the indemnity for a [web-design services agreement] under [English] law from the [service provider's] side. Version 1 [CLIENT-FAVOURABLE]: customer indemnifies provider for third-party IP claims arising from customer-supplied materials; provider gives none. Version 2 [MARKET-STANDARD]: mutual indemnity limited to third-party IP infringement claims, each subject to the cap in clause [X]. Version 3 [AGGRESSIVE - EXPECT PUSHBACK]: Version 1 plus a duty to defend.
For each: the clause, its assumptions, and the counter-argument the other side will raise. Cite no case or statute. Draft no other clause.

Long documents and files: Cowork vs Projects

Current Claude models (Opus 5, Opus 4.6 to 4.8, Sonnet 4.6 and 5) have a 1M-token context window, and one request can carry up to 600 images or PDF pages. Anthropic’s own docs add: “more context isn’t automatically better. As token count grows, accuracy and recall degrade, a phenomenon known as context rot.” Chroma’s study of 18 models found even one distractor hurts. Ten relevant documents beat a hundred assorted ones on either tool.

Both products have Projects, a standing workspace with instructions and knowledge files where a playbook lives; Claude Academy’s NDA set-up tests it on “3-5 previously reviewed NDAs”, and Claude Projects and custom GPTs for law firms walks through the build.

Cowork is the genuine difference. Zack Shapiro, whose February 2026 post on his two-person Claude-run firm drew over seven million views, calls it the mode most lawyers have not tried: “I point Claude at a folder on my computer, give it a task, and it goes and does it.” A sceptic on r/legaltech is fair too: “$20 is fine, but the real tier is $200, and it’s still not a legal tool”.

Before answering, extract into <quotes></quotes> every passage from the attached documents relevant to this question: [does any agreement give the counterparty a change-of-control termination right?]. Give each quote its document name and clause reference. If none exists, write <quotes>NONE</quotes> and stop.
Then answer using only those quotes, referencing them by number. Label anything not traceable to a quote as INFERENCE.

Research and Deep Research

For open-web research the picture flips. OpenAI’s Deep Research, launched 2 February 2025, returns cited reports in five to thirty minutes and is the tool the prompt library points to for a first-hour regulatory briefing. Every research agent’s bias “is to search efficiently, not completely” (Harvey), so ask it what it did not find.

On accuracy the general model holds up. In Vals AI’s October 2025 legal research benchmark, as reported by LawSites, ChatGPT scored 80% against a lawyer baseline of 71%, but 70% to the legal tools’ 76% on “authoritativeness”. None of that makes either chatbot a citation source: the Divisional Court in Ayinde v Haringey said freely available tools “are not capable of conducting reliable legal research”. Use either model for the elements, the search queries and the adversarial pass; get the authorities from a database with a citator. One r/legaltech lawyer feeds each tool’s answer to the other “telling it to review it with scepticism and make an independent assessment”.

Here is a research memo produced by another AI system: <memo>...</memo>. Attack it. Identify every proposition that is overstated, every authority likely to be misgrounded (real but not supporting the point), every counter-authority a diligent opponent would raise, and every assumption that, if false, collapses the analysis. Add no citations of your own; describe what authority should exist. Finish with the three claims I should verify first.

Hallucination behaviour: abstaining vs forcing an answer

The best comparative data concerns what each model does when unsure. Chroma’s July 2025 study of 18 models found Claude models had “the lowest hallucination rates” with distractors and “tend to abstain when uncertain”, while GPT models showed “the highest rates of hallucination”. Lin Li’s analysis of reasoning models agrees: OpenAI models had “significantly lower non-response rates and simultaneously higher hallucination rates compared to the latest Google Gemini and Anthropic Claude models”. Anthropic’s interpretability work found that in Claude “Refusal to answer is the default behavior”, overridden when a name is familiar but the facts are not: a case name that sounds right is exactly that misfire.

Confidentiality tiers compared

The distinction that matters is consumer versus commercial tier, not OpenAI versus Anthropic. Is ChatGPT confidential for lawyers? covers the OpenAI side.

In United States v. Heppner (S.D.N.Y., February 2026) Judge Rakoff held that a defendant’s roughly 31 documents of consumer-Claude exchanges, made without counsel’s direction, attracted no privilege and no work-product protection: “Because Claude is not an attorney, that alone disposes of Heppner’s claim of privilege.” The SRA’s warning notice of 17 August 2026 says the same of public tools generally: privilege “may be permanently waived and unable to be recovered”.

EU data residency: ChatGPT Enterprise vs Claude via Bedrock

For firms in Germany, Austria, Switzerland and much of the EU this settles the question, against Claude’s first-party service. OpenAI has offered at-rest EU residency for new ChatGPT Enterprise and Edu workspaces since early 2025, in-region zero-data-retention processing for API projects in its Europe region and, from 16 January 2026, an in-region inference option for eligible Enterprise customers (OpenAI). Anthropic’s data-residency documentation offers inference in “global” or “us” and states that “us” is the only available workspace storage location. EU processing of Claude exists only through AWS Bedrock or Google Cloud Vertex regional endpoints, where the hyperscaler is your processor. And for Copilot users: “Anthropic models are currently excluded from the EU Data Boundary.”

The CCBE’s technical guide adds the contractual point: “Whether a prompt is later used for model training depends not on the model architecture itself, but on the provider’s contractual terms.” A DACH firm that wants Claude buys it through Bedrock or Vertex, or through a platform that does; a firm that wants first-party chat with EU storage buys ChatGPT Enterprise. More in EU data residency for ChatGPT, Claude and Copilot.

Word integration and tracked changes

Claude for Word entered beta on 11 April 2026 for Team and Enterprise plans only, with native tracked changes. Anthropic’s example prompts include “Make the indemnification mutual and insert our standard fallback language” and “What did the counterparty change, and which revisions are dealbreakers?” (Artificial Lawyer). Stephen Smith’s 30-page test kept numbering and defined terms intact: “every change Claude makes shows up as a native Word tracked revision. Deletions in red. Insertions in green.”

His limits: prompt-injection risk from counterparty documents, no persistent chat history, no Enterprise audit logs yet, 30-day deletion. One r/legaltech user: “Claude MS Word plug-in doesn’t even come close to Spellbook.” And redlining is the one task where Vals found lawyers still beat every tool, 79.7% to 65.0%.

Price for a solo and for a five-lawyer firm

List prices are verified against the vendors’ pages as of September 2026.

For a solo the choice is consumer versus commercial: a $20 seat for learning and marketing drafts, a $20 to $25 Business or Team seat as the floor for anything touching a client. Five standard seats cost $1,200 a year on either side; both together, $2,400 to $3,000. On the r/legaltech pricing thread, where Harvey was quoted at $1,200 per user per month, one commenter wrote that “Claude at $100 per month has been robust for us”.

The switch stories, both directions

Traffic runs the other way too. On the September 2026 r/legaltech “AI Tools for Law” thread one lawyer wrote “I used to have ChatGPT Pro, but it hallucinated too much” and moved to Clio’s Vincent AI, not to the other chatbot. An assistant general counsel there: “We already have Claude and said no to Harvey and GC AI.”

The vendors flatter both. Thomson Reuters built its next-generation CoCounsel Legal (20 August 2026) on Anthropic’s Claude Agent SDK; Harvey ran Claude Opus 4.6 live from 5 February 2026 while its benchmark had crowned GPT-5 the previous summer. The r/legaltech shorthand “Legora = Claude, Harvey = GPT” is too neat, but the four-figure platforms wrap the same two families.

In AI Lab for Lawyers we run the same task, an NDA review against a playbook or a chronology, in ChatGPT and in Claude on screen, and you judge the outputs. Where to go next: ChatGPT for lawyers and Claude for lawyers go setting by setting, Gemini for lawyers covers the third candidate, and the tools hub compares the platforms built on them.