Passphrase vs password: which is stronger and easier to remember?

How this is calculated

The strength of a passphrase depends on the word list size and the number of words. With a 7,776-word list (the EFF long word list), four words give 7,776^4 ≈ 3.66 × 10^15 combinations (about 51 bits of entropy). Five words give 7,776^5 ≈ 2.8 × 10^19 (about 64 bits). Six words give 7,776^6 ≈ 2.2 × 10^23 (about 77 bits). A six-word passphrase is stronger than any password a human could reasonably memorize. The downside: passphrases are longer to type and some sites still enforce character-class requirements (uppercase + lowercase + number + symbol) that passphrases don't meet without modification. Add a number and a symbol as a word separator or suffix to satisfy those requirements without sacrificing memorability.

Verdict

Use passphrases for passwords you need to remember and type (master password, computer login, disk encryption). Use random passwords from a password manager for everything else. A 4-5 word passphrase is both memorable and strong enough for most threat models.