Yes, that use case sounds very much like what Profiles are for. You'll find that Profiles are an improvement over Containers for tasks like that (logging into the same URL as different identities) for all the reasons I list above.
> Way better than opening one is FF, one in Chrome, etc
> Yes, that use case sounds very much like what Profiles are for.
I'm not quite sure how profiles work in Chrome, but from a Firefox point-of-view this is only true if you also want to keep your history/bookmarks/settings/add-ons completely separate, too.
Yes, history, bookmarks and extensions are separate. I have one profile for "me in my personal life" and "me at work", and a few for testing logins to different interfaces at work. So this degree of separation is mostly what I want, although it can be a little annoying to maintain the extensions you want under both profiles.
Keeping history separate in particular is very valuable since nowadays the fastest / least hassle way to bring up a site is to start typing the beginning of the URL in the navigation bar, so you wouldn't want work URLs mixed in with non-work URLs.
> Way better than opening one is FF, one in Chrome, etc
Agreed!