Here's the honest split between these two: they're not really competitors — they're best at different moments.
Notion AI wins when…
…the work lives in your docs. Summarizing a meeting note, turning a page into action items, rewriting a section, or querying your own workspace — Notion AI is right there in context, no copy-paste. For team knowledge, it's the smoother tool.
ChatGPT wins when…
…you need raw capability: complex reasoning, coding, longer creative work, images, voice, and the flexibility to go anywhere. It's the stronger standalone brain.
How to actually use them
Reach for ChatGPT for thinking, drafting, and problem-solving; use Notion AI to turn your existing docs and notes into finished, organized output. Together they cost about $30/month and replace a surprising amount of busywork.
Verdict
If your work is document-heavy and team-based, Notion AI earns its keep. If you want the most capable general assistant, ChatGPT. Most power users happily run both.