The biggest difference is that Bazzite uses Fedora Atomic as opposed to the “Workstation” Fedora base. Nobara’s filesystem does not have read-only root files while Bazzite does.
Bazzite shares packages with Nobara and other similar projects like ChimeraOS. Bazzite maintainers and contributors have also collaborated with both projects previously. Arguably, Nobara and Chimera are most likely much more mature by now since they were here longer, and Bazzite is not even a year old yet (at least in terms of the first official public release.)
Our Github README includes what packages are part of Bazzite if you are interested. The best way to see the difference would be trying Bazzite in a virtual machine before trying it on bare metal especially if you do not have any issues with using Nobara currently. Also check out our documentation for more information.
Edit: Basically, what I am trying to stress - if any of the similar projects (Nobara, ChimeraOS, etc.) work fine for your setup, then I would only try Bazzite in a VM if you’re curious about it and take it from there. Other maintainers, contributors, and I probably cannot give anyone a list of pros/cons of each OS. It’s basically preference and what works for you.