A notebook is better in some ways, but worse in important ones. It can't save you from phishing, and your password strength is going to be relatively poor (since a notebook can't generate them for you, and if they get long it'll be annoying to type). Also, a notebook is easier to copy, steal, or lose (though this is a fairly minor consideration for most people).

I would say a notebook is worse than a password manager. It's not strictly worse in every way, but on the balance it's not a hard choice.

A notebook is better than most other not-a-password-manager solutions though. So it has that going for it.

And less resilient.

If your notebook is destroyed (e.g. dog eats it, fire, water damage, et al) then all your passwords are gone. With most good password managers you can actually backup and store a copy of your vault data locally.

The notebook is still less secure because of phishing