If I understand correctly, these only compartmentalise cookies and browsing history, whereas full profiles (via the -ProfileManager switch in Firefox) compartmentalise the whole browser config (add-ons, permissions, etc.) as well, which I think is much more useful.
I use distinct profiles for testing, but during the day, I open versions of the site for personal and work for example. Or at work for different clients.
It depends on workflow IMO. There are uses for both.
To me it's the opposite. I'd like the same browser config, use the same window, keep my bookmarks, history etc., just want different logins and website contexts. I love Firefox's implementation of containers, and find Chrome's way of doing profiles useless.
But Firefox supports profiles as well if that's what you want, as you say. So best of both worlds.
Given that Firefox already has multi-profile support internally, it would only be a matter of adding a GUI similar to Chrome's to make it the best of both worlds.
