One scenario: have a profile for each client so that you can open any website in the context of your work for that client.

Containers then can be used to separate multiple logins into the same website: e.g. you're testing a multi-user app and want to login as admin and user at the same time - containers make that easy without having to mess with incognito/private modes (those will forget your login as soon as you close them).

Profiles for the typical Work/Personal separation with their own bookmarks, extensions, password manager accounts etc……

Then I use containers for isolating sensitive accounts within those profiles (bank, work Google Drive, etc).

I also use temporary containers to make it easier to be logged into the same site with multiple accounts at the same time between tabs - like admin and user accounts for our company’s app - which also make it easier to clear sessions and data.

https://addons.mozilla.org/en-US/firefox/addon/temporary-con...

The growing consensus seems to be: containers are what services you want to separate from each other (cross-service tracking cookies, etc) and profiles are what services you want to separate for yourself (workflows/projects/work versus fun, etc).