Profiles provide separate bookmarks and add-ons per profile. I don't think containers do. Containers seem to be more about making it so you can appear as different people to different sites. Profiles are more about letting you separate roles.
For different things I do during development, I want different sets of cookies, bookmarks, history, and add-ons. With profiles, I get that, effectively getting a separate browser that I can extensively customize to its particular task.
Those were actually what I was thinking of when I said Chrome handles profiles better. Firefox has the functionality, but it doesn't have as nice an interface to it. Chrome, for example, on MacOS puts the available profiles on the right-click menu on its dock icon.
For different things I do during development, I want different sets of cookies, bookmarks, history, and add-ons. With profiles, I get that, effectively getting a separate browser that I can extensively customize to its particular task.