I'm a recent convert to 1Password from Keychain but this statement is simply untrue if you have ever looked at the Keychain preferences. For any keychain on the Mac you can choose a separate password than your login password, and, you can set what time period can elapse before it will lock (same as 1Password). If Keychain is properly used it is no less secure than 1Password. In either use-case you simply cannot walk away from your Mac unless you have locked Keychain or 1Password first.
With that said, 1Password is certainly more secure and convenient than using Keychain in conjunction with browsers like Chrome (yes Chrome does use Keychain). I'm loving 1Password and appreciate the polish, security, and support it provides.
Yes, I can set a different *keychain* password. But when you use Safari to save a web password, you do not ever go into keychain or need to worry about keychain. If Safari saves the web login, you only need to open Safari, go to a site, and Safari enters the info. With Safari saving passwords, you do not have to type in a password at first launch, such as you do with 1Password.