Saving passwords within your browser is never a good idea. Per our password manager guide, you are much better off storing passwords here than within the browser itself.
The reason why it is a bad idea is because of how easy it is to view passwords in modern web browsers. Google Chrome will allow users to view saved logins, even without requiring a user password (unlike on Windows and macOS, where a user password is required). Firefox, on the other hand, gives instant access to those passwords, without authentication, regardless of platform (unless a master password is set).
For this reason, your passwords are much less secure and at a greater risk of being taken if there is a breach in security while you are online. Additionally, if you are running an outdated version of your browser and have passwords saved there, the risk only increases.
Always make sure to keep your browser up to date and never save your passwords directly within your browser!