I think this is a relative question. For now, you can add to your list:
- Filament
- Backpack
- Lean-Admin (not out yet but looks promising)
Also please note Nova isn't free. A license is required. Backpack has a free non-commercial tier. If I was you, I would consider a commercial panel. There's no such thing as a free lunch, unless you're very lucky.
In the case of Nova, which is incredibly popular, you could leverage its packages via NovaPackages. This could save one years in coding. But if you're more into the TALL stack instead of VueJS and you want to extend the panel, you might go for Filament or Lean-Admin.
The best is to test drive a few and see what works. What makes you happy and productive. My personal preference is Nova because of NovaPackages but I'm not a huge fan of VueJS. A big reason why I'm also so committed to Nova is because some really clever guy figured out how to make it multi-tenant without paying for another license.
Finally, there is a "rumor" that a new Nova is on the way. That would be worth watching as Nova is created by some of the top guys in the community (including Taylor Otwell and David Hemphill). I guess I'm hanging to find out if the new Nova is Livewire or Inertia.JS as I would like to settle on one stack for my back offices for the next few years. When the original Nova came out, I thought VueJS is it, but that's before Livewire and Inertia.JS.