When comparing pwgen vs LessPass, the Slant community recommends LessPass for most people. In the question“What are the best password generator add-ons for Firefox?” LessPass is ranked 2nd while pwgen is ranked 3rd.
Ranked in these QuestionsQuestion Ranking
Pros
Pro It's simple to use
All you have to do is click on the small P icon and a password is instantly generated, shown and copied into your clipboard.
Pro Open source
Pro Really platform-free
Works everywhere, in any device that can run javascript.
Pro Doesn't store passwords
If it's not stored, it can't be stolen.
Cons
Con Deterministic
Deterministic password managers have many drawbacks.
Con Cannot store existing secrets
Existing secrets (aka passwords) cannot be stored with deterministic password managers. In order to use LessPass effectively, you will need to change your password on every site.
Con Easily cracked with exposed/compromised master password
Since anyone can use LessPass with the same parameters as you, all they need is your master password (which could be obtained through keylogging or numerous other methods) to gain access to every one of your site passwords.