Maybe I haven't looked too deep into Firefox multi-profile config, but:

- The distinction between pinned (soft-bookmarked) tabs and other tabs is very useful for me organizing things at work. (I didn't like when Arc added a setting to auto-delete other tabs X days after creating, though)

- Multiple "spaces" on the tab bar combined with global bookmarks at the top mean I can have a space for planning work and one for implementation work, and from both of those I have an easy link to Jira to search up tickets without needing to hop back and forth.