Direct answer
Choose by use case, privacy, source control, retrieval needs and repeatability. NotebookLM is useful for source-grounded exploration. ChatGPT is flexible for drafting and reasoning. A Custom GPT can package repeatable instructions. A private knowledge pack is better when you need portable, governed source material across tools.
Why it matters
This answer explains how messy notes, files, research and AI context become a structured, source-aware knowledge asset. The value is not more files; it is selection, boundaries, retrieval, review and reuse.
What to check
- What is source material, what is synthesis and what is final customer-facing output?
- What should be excluded for rights, privacy or quality reasons?
- How will the pack be reviewed, updated and tested?
Common mistake
Uploading everything into an AI tool and calling it a knowledge base without source roles, exclusions, versioning or retrieval tests.
Caveats
Medium caveat risk: use careful wording and recheck current, technical, platform, service-scope or public-account claims before publication. Keep the answer framed as guidance rather than a guarantee.