I recently investigated best-practices in regards to passwords, and the overwhelming majority of sources recommended using a password manager. This is great advice, but not usable in every situation. Certain situations, such as OS login, Disk Decryption or Password Manager unlocks do not allow me to let a password manager "type my password in for me".
As such, I have looked at the second-best alternative, which seems to be Diceware and Passphrases. What had me stumped was this answer of a related question, which hinted that Diceware was superior. An excerpt from the answer:
Passphrases are great (Diceware is better) for locking password managers, [...]
What confuses me is why this claim that Diceware is supposedly superior? I used zxcvbn to compare the strength of the two example passwords below and it seemed as if the passphrase was more secure than the Diceware password. Further, the Passphrase generates a visual image, although nonsensical, which is easy to remember. The only disadvantage I can imagine is that the passphrase takes longer to type, which is a marginal disadvantage considering it would only need to be typed once before a password manager can be used again.
Diceware is the process of rolling a set of dice, which would indicate a random word from a pre-defined list. Depending on the desired security, more words are chosen.
An example outcome of a Diceware process might be the password:
cleft cam synod lacy yr wok
A passphrase is in essence a sentence, which make sense to the user and hopefully nobody else. It might make grammatical sense, but is very unlikely to make semantic sense.
An example of a passphrase would be:
Blue Light shines from the small Bunny onto the Lake.