I've opted for profiles. With profiles, it's like getting a completely new browser. You start off with the default about:config, preferences and no extensions.
The way my main FF browser is set up, I have multiple privacy enhancing extensions (including uMatrix), highly modified config, tightening of privacy preferences, WebRTC off, service workers disabled, telemetry disabled, etc and etc... This can create some problems on sites that pour hundreds of millions into tracking, data-collection.
So I have additional profiles that are Amazon-specific, Google-specific. If I facebook'd, I'd have a profile for them too. Each of these domain-based profiles are far more liberal (minimal extensions and such; fewer config tweaks). I even have a profile that's 100% Private Mode (ie, history, cookies... deleted after shutdown) with it's own set of config tweaks and extensions.
I use my privacy-enhanced default FF for most sites w/o issues. I wanted Google and Amazon completely separate while providing them more access to my browser (so that I could enjoy the full web experience without worry that a browser issue would make it easy for them to steal my entire browser usage). So they're free to rummage around, read cookies, access APIs - but they're only getting their own stuff back.
I feel profiles provide a better defense (all settings, cookies, storage in their own subDirectory) and much more flexibility than containers.
Functionality is similar, but containers are a lot easier to manage than profiles in FF for me. Everything is right in the container icon and you don't have to re-login like when setting up profiles. You can create new containers and remove unused ones in a couple of seconds vs profiles which are much slower to manage.
I don't bother with profiles any more, especially since there's a one click option to open all the container tabs in a new window as well.
The huge downside with them is they don't sync across devices. If/When this comes they will be perfect.
Is the only different between this containers vs profile the container is tab base vs profile will be different windows?