Both ship strong consumer chat experiences, both have voice + image in the box, both have credible coding assistants. ChatGPT's edge is the depth of its third-party ecosystem — Custom GPTs, Operator, the agent SDK, broader plugin support. Gemini's edge is context (1M+ tokens usable, not just advertised) and the Workspace + Vertex integration story.
For a small team: pick whichever ecosystem you already live in. For a builder shipping new product: ChatGPT's ecosystem density usually wins.