I would not declare ChatGPT, Claude, or Gemini the writing winner without running my tasks: emails, landing pages, support macros, blog drafts, and executive summaries.
ChatGPT
Broad, familiar, strong plugin ecosystem.
Often a team default.
Claude
Many teams like it for long docs and careful tone.
Gemini
Strong if you live in Google Workspace and want research tied there.
Picking
Run blind tests on three pieces.
Score edit time and factual errors.
Standardize prompts.
The best writing model is the one your team edits least while staying accurate. Rotate models for high-stakes copy if you want a second opinion.