Here’s the irony: Copilot runs on OpenAI’s models, yet it’s a different product than ChatGPT. Microsoft wrapped that intelligence in Word, Excel, Outlook and Teams, while ChatGPT stayed an open-ended chat tool that goes anywhere. So the real question isn’t “which model is smarter” — it’s “do you want AI inside your documents, or AI as its own workspace?” I used both across a month of actual work to find out. The quick verdict Best inside Microsoft 365: Copilot — nothing else touches your real files like this. Best standalone chat & flexibility: ChatGPT — more capable, more open. Best for coding: ChatGPT — deeper, less constrained. Best free tier: Copilot — surprisingly capable for free. Round 1: Working inside documents I asked both to summarize a long Word doc and draft a reply based on an Outlook thread. Copilot did this natively — it read my actual file and inbox and acted on...