Those are for different things. I use containers to log in to the same website with different accounts without having to switch browsers or open a new window. E.g., since Discord still doesn't support switching accounts in the year of our lord 2021, I have a container set up for the discord account I use for IRL stuff, and my personal account logged into the "vanilla" container. I can keep both discord tabs open side by side and get notifications from both.
Even for websites that allow switching accounts, I prefer to use containers especially if the accounts go across different "domains" of my life. If I must log in to something personal at work or vice versa, I generally use a container for that to keep them separate.
I use containers to only use some google services while signed in. For instance I use gmail signed in but I google search in a separate container to not log that data in my account.
I may be fooling myself and google can identify it anyway through my IP or something but it feels like I get a little extra anonymity.
I use ddg primarily, but I regularly need to use g! to reroute myself to Google when searching for anything that I don’t already have domain-specific knowledge for.
Like if I want to just check syntax for a new programming language, ddg can handle the search just fine, but if I am doing initial research for a problem I don’t understand well, I need Google to get consistently relevant results.
But the search is not as good. Or good might be subjective in this case. But I tried using DDG mutliple times, but every time I end up just doing the same search on google becouse it is much better at giving me the result I want.
Earlier this year when PS5's were really hard to get, I used Firefox Containers to help get one. One of the tracking services would tweet that some retailer had them for sale. I would use containers to open a dozen connections to the server. A couple containers would get through and eventually I was able to complete the purchase transaction.
It took about a week of trying and I was successful at Walmart and BestBuy.
I wrote up a quick email to friends/family at the beginning of the pandemic about Firefox containers in regards to the vaccine signups that were occurring. Since there was site isolation you could get as many “slots” as you were willing to solve capchas. Most of my friends and family were vaccinated because of this feature. A bunch say they use it now a days for normal site isolation but I did at least convert some people off chrome that way.
You would think but no. Open a private window and log into a site. Then open another and it’ll be logged in. Incognito windows share cookies. They are deleted once incognito mode is turned off but that doesn’t help us in our “open 100 windows at the same time to get a bunch of slots” use case here.
Even for websites that allow switching accounts, I prefer to use containers especially if the accounts go across different "domains" of my life. If I must log in to something personal at work or vice versa, I generally use a container for that to keep them separate.