I use http://www.alexhornung.com/2014/01/15/introducing-bpasswd2/ because it doesn't store anything anywhere except some settings for some sites that need different options when generating the password.
If the site's password is always a function of the master password and the site URL, what do you do when a site was breached and you need to change its password? What if the site changes URL (eg twttr.com became twitter.com)?