Hi there @briane!
Thanks for posting in our community!
The biggest difference right now between the two is the layout. You can get the same info from both if you are looking for updates.
One difference is that you can export your case list from PowerSource which you can't do in the Case Portal.
I would recommend going with the Case Portal now that we have it since it is also where a lot of the other documentation resources are.
Hopefully that helps you in your decision making process!
At this time, your site-wide cases can be viewed in PowerSource. We will continue to make updates to our Community case portal and share those updates here.