GPT-5 vs Claude 4.6 for Summarizing Long Documents
Which model produces better summaries of lengthy reports, research papers, and legal documents? We run detailed tests.
Why Summarization Quality Matters
Summarization is one of the most practical AI applications in business. Executives summarize reports, researchers condense papers, lawyers extract key clauses. A good summary saves hours; a bad one can cause costly misunderstandings.
We tested GPT-5.2 and Claude Opus 4.6 on 100 documents across three categories: academic research papers, legal contracts, and business earnings reports. Each summary was evaluated for accuracy, conciseness, and preservation of critical details.
Research Paper Summaries
Claude Opus 4.6 produced superior research paper summaries, scoring 91.3% on our accuracy metric vs GPT-5's 87.6%. Claude consistently captured methodology details and limitations that GPT-5 sometimes omitted. Its summaries also better preserved the nuanced conclusions that researchers care about.
GPT-5 summaries were more readable and better structured, but occasionally simplified findings in ways that a domain expert would consider inaccurate.
Legal Document Analysis
For legal contracts, Claude dominated with a 94.1% accuracy score vs GPT-5's 88.9%. Claude's safety-first design translates directly to legal summarization: it's more likely to flag ambiguous clauses, note potential risks, and preserve legally significant language.
GPT-5 produced cleaner executive summaries but missed subtle provisions that a lawyer would consider material. For legal work, Claude is the clear winner.
Business Reports
GPT-5 edged out Claude on business earnings reports, scoring 90.2% vs 88.7%. GPT-5 better extracted financial metrics, highlighted quarter-over-quarter trends, and produced summaries in the format that business analysts prefer.
For board-ready executive summaries, GPT-5's assertive style is actually an advantage—it states conclusions clearly rather than hedging.
Context Window Impact
GPT-5's 256K context window means it can process most documents in a single pass. Claude's 200K window is also generous but falls short for the largest legal filings and research compilations.
Both models degrade gracefully with very long inputs, but GPT-5 maintains higher consistency across 150K+ token documents.
Verdict & Recommendation
Use Claude for research and legal summarization where accuracy and caution are paramount. Use GPT-5 for business reports and executive summaries where clarity and assertiveness matter more.
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