The short answer
If your company runs on Microsoft 365, Copilot usually wins on fit: it works inside Word, Excel, PowerPoint, Outlook and Teams, only shows people data they already have permission to see, and Copilot Chat comes with your Microsoft 365 business plan.
If your company doesn't run on Microsoft 365, most of that advantage disappears, and ChatGPT can be the simpler choice.
One change affects every ChatGPT team this year: custom GPTs retire on December 11, 2026, so the GPTs you rely on need rework either way.
Source: OpenAI Help Center: Custom GPT retirement and migration FAQ
- CopilotInside Microsoft 365 apps, grounded in your Microsoft 365 data and permissions
- ChatGPTIts own apps, working with what you upload or connect
- Dec 11, 2026Custom GPTs retire on all ChatGPT plans
Copilot vs ChatGPT, side by side
Business plans only: ChatGPT Business and Enterprise, and Microsoft Copilot (formerly Microsoft 365 Copilot).
| Topic | ChatGPT Business and Enterprise | Microsoft Copilot |
|---|---|---|
| Where people use it | ChatGPT's own web, desktop and mobile apps | Inside Word, Excel, PowerPoint, Outlook and Teams, plus Copilot Chat |
| Company data it can use | Files and apps you upload or connect to it | Your Microsoft 365 mail, files and meetings, within each person's existing permissions |
| Custom assistants | Custom GPTs, retiring December 11, 2026; plugins replace them | Copilot agents in Agent Builder (instructions up to 8,000 characters, up to 20 files) or Copilot Studio |
| Connecting other systems | Connected apps and actions (custom actions don't carry over to plugins) | Copilot Studio connectors and MCP servers |
| Models | OpenAI models | Models Microsoft selects for Copilot, including Anthropic's Claude models in most commercial tenants |
| Training on your data | OpenAI says business data isn't used for training by default | Microsoft says prompts, responses and Microsoft Graph data aren't used to train its foundation models |
| Admin and compliance | ChatGPT workspace admin; Compliance Platform on Enterprise and Edu | Microsoft 365 admin center, Microsoft Purview, enterprise data protection |
| Exporting your data | No self-service export on Business and Enterprise | Stays in your Microsoft 365 tenant |
| Cost | A separate subscription per seat | Copilot Chat included with Microsoft 365 business plans; the full license lists at $30, or $21 for Copilot Business under 300 users |
List prices change and agreements differ. The cost calculator compares your own numbers.
When each one fits
Not every team should move everything. These are the patterns we see in assessments.
Copilot fits best when…
your company already runs on Microsoft 365, your work lives in SharePoint, Outlook and Teams, and you want one AI tool under the same security and compliance as everything else.
ChatGPT fits best when…
your company doesn't use Microsoft 365, or a small group relies on something ChatGPT does that your Copilot rollout doesn't cover yet. The assessment shows where that line is.
Most companies end up…
consolidating on Copilot for most people, rebuilding the GPTs they depend on as Copilot agents, and retiring the rest before December 11.
Four questions that settle it
Where does your work live?
If it is in Microsoft 365, Copilot can use it in place, with your existing permissions.
What are you paying twice for?
Count the AI seats you pay for on top of Microsoft 365, including the ones on expense reports.
Which GPTs can't you lose?
They need rework before December 11 either way: as an OpenAI plugin or as a Copilot agent.
Who needs to control the data?
If IT, security or compliance need one place to manage AI use, a tool inside your Microsoft 365 tenant is simpler.
Questions we hear most
Is Microsoft Copilot the same as Microsoft 365 Copilot?
Yes. Microsoft renamed Microsoft 365 Copilot to Microsoft Copilot, and Microsoft 365 Copilot Chat to Microsoft Copilot Chat.
Is Copilot just ChatGPT inside Microsoft?
Copilot is Microsoft's own product: it runs inside your Microsoft 365 tenant, grounded in your data and permissions, under Microsoft's security and compliance controls. In most commercial tenants it can also use Anthropic's Claude models.
Can we move our custom GPTs to Copilot?
Yes, by rebuilding them. There is no import, but each GPT's instructions, files and actions map to a Copilot agent. Try the convert step in the chat above with one of your GPTs.
Does Copilot train on our data?
Microsoft says prompts, responses and data accessed through Microsoft Graph aren't used to train the foundation models used by Microsoft Copilot.
Do we need a paid license for everyone?
No. Copilot Chat comes with Microsoft 365 business plans at no extra cost. The paid license adds Copilot across Word, Excel, PowerPoint, Outlook and Teams with your company data.
Is eMazzanti affiliated with OpenAI or Microsoft?
eMazzanti Technologies is an independent IT services company and a Microsoft partner, and offers this service with Messaging Architects. Neither is affiliated with or endorsed by OpenAI.
Who does the work
eMazzanti Technologies is an IT services company and Microsoft partner, and runs AI migrations together with Messaging Architects. A few things we have done before:
Microsoft partner
Named Microsoft's SMB Worldwide Partner of the Year, with Modern Work and Azure specializations.
A New Jersey Best Place to Work
Named one of New Jersey's Best Places to Work for 2026 by NJBIZ, based on a confidential survey of our own team.
We teach Copilot
eMazzanti runs Microsoft Copilot Master Classes for business teams. The training step of every migration comes from the same people.
The migration process was flawless, with zero downtime, and their cost-effective solutions have significantly enhanced our operational efficiency.
There's absolutely no hesitancy for me to recommend eMazzanti to anyone.
Keep reading
See your plan before you commit to anything.
The chat at the top builds a migration outline for your team in about two minutes. When you are ready, an eMazzanti migration lead walks through it with you.