The right choice depends on where your firm’s work already lives.

Neither vendor publishes a test on documents like yours, so the answer has to come from your own. Two facts shape it. Claude’s plans give a context window of up to 1M tokens, varying by model, which is room for a full CIM, the credit agreement and its amendments in one conversation. ChatGPT for Financial Services adds citations that trace a figure back to the table or passage it came from, for the data OpenAI hosts.

Both will give a confident wrong answer on a document your team knows well. Take one closed deal, ask each tool twenty questions your team already knows the answers to, and count the misses. That afternoon tells you more than any review, ours included. Our guide to making AI accurate on investment documents sets out the test.

Neither company trains on business data by default: Anthropic says so on Claude’s Team and Enterprise plans, OpenAI on ChatGPT Business and Enterprise.

Retention is where the plans differ. Claude Enterprise lets an Owner set a custom retention period, 30 days at the shortest. Without one, chats and projects are kept indefinitely, and the setting does not reach Claude Design, Managed Agents or Claude Code in the cloud. Claude’s Team plan has no custom retention. On ChatGPT, OpenAI lists retention control for Enterprise, not Business. ChatGPT for Financial Services adds separate workspaces to enforce information barriers and exports workspace logs for compliance; Claude Enterprise has audit logs and a Compliance API.

Before either goes near live deal documents, write down what staff may upload. Our AI usage policy guide covers MNPI and LP data.

On Claude, the Team plan has SSO and admin controls for connectors. Enterprise adds SCIM provisioning, audit logs, the Compliance API, role-based access and custom retention. On ChatGPT, Business covers teams of 2 to 200 with SAML SSO and MFA. Enterprise adds SCIM, role-based access and configurable retention, and the financial services product adds compliance log exports.

If your compliance team or an LP could ask who saw a document and when, you need Enterprise on either side. A ten-person deal team piloting on non-confidential work can start on Team or Business and move up once the policy is written.

Claude has add-ins for Excel, PowerPoint and Word, generally available since 5 May 2026, with Outlook announced as coming. ChatGPT for Excel and for Google Sheets became generally available on every plan the same day; it links its answers to the cells it uses and asks before it changes a workbook. ChatGPT for Financial Services also lets admins publish the firm’s own Excel, Word and PowerPoint templates, so models and pitch materials come out in house format.

If your firm runs on Microsoft 365 Copilot, there is a third route. Microsoft added Claude Opus 5 to the model selector in Copilot in Word, Excel and PowerPoint on 24 July 2026, alongside the OpenAI models Copilot already ran. A firm with Copilot already deployed can try both before buying either.

Both, in different ways. Claude has connectors for FactSet, S&P Capital IQ, MSCI, PitchBook, Morningstar, Chronograph, LSEG and Daloopa, and added SS&C Intralinks, Third Bridge, Guidepoint and others in May 2026. They work for firms that already subscribe to those providers.

ChatGPT for Financial Services includes datasets from Daloopa, PitchBook, LSEG News and Crunchbase, hosted by OpenAI, with no separate contract to sign. OpenAI is building shared sign-in with S&P Capital IQ, LSEG, MSCI, Factiva and Moody’s, and lists 50+ connectors including Datasite, Preqin, FactSet and Intapp. It is sold to eligible financial institutions, and OpenAI says it starts with investment banking and equity research.

Less than the plan around it, and it changes faster. Claude runs Anthropic’s models only; Claude Opus 5.5 arrived on 22 September 2026. ChatGPT runs OpenAI’s only; GPT‑6 Astra arrived in September 2026, with Enterprise access off until an admin turns it on. Either lead can change within a quarter. Microsoft 365 Copilot is the one place in this comparison that offers both families, subject to region and tenant settings.

Choose on the plan, the controls and where your team already works. Expect the model to change before the contract renews.

Four situations cover most firms, and each has a different first move: