I figure I could either use a secure password manager to generate a long, randomly generated password for my keystore file, or could come up with a less secure passphrase that I memorize. Which method would be better, both in terms of safety and risk of losing access to my wallet?
Contrary to popular belief, long randomly generated passwords are no more secure against brute-forcing than long, easy to memorize passwords. However, it is essential that you don't utilize any personal information or common passwords.
is just as secure to pure brute-forcing as:
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However it is often common to find password requirements on websites that require you to include numbers and symbols, which are often not that useful, more difficult to remember, and even sometimes less secure.