What are some alternatives?
When comparing Open Tabs and Multifox, you can also consider the following products
Tabs Outliner - Next Generation Session, Windows, Tabs Manager and a TooManyTabs Solution That Really Works.
Firefox Multi-account Containers - Sign in to two different accounts on the same site
OneTab - Whenever you find yourself with too many tabs, click the OneTab icon to convert all of your tabs into a list. When you need to access the tabs again, you can either restore them individually or all at once.
Multiloginapp - Connect to websites as a multitude of different users
Session Box - Using websites with multiple accounts at the same time is made easy.
Tab Mix Plus - Tab Mix Plus enhances Firefox's tab browsing capabilities.