The difference is, most of System76’s laptops are barebones models from Clevo, whereas Purism designs its own laptops.
My understanding is they've started selling their own desktop models after selling white-labeled machines in the past. And that with laptops they are quite involved in the design process and are inching towards selling their own custom laptops.
If Purism fails it will likely be because they did too much from scratch. Taking on hardware and software all at once is a recipe for disaster. It's super expensive.
Hell, for Purism's laptops it's not uncommon for people to shove in a different wifi card to get modern speeds - the card they use is used for being able to run with only open source drivers, which are old at this point.
The complete open hardware model seems to require DIY chip fabrication at some level as a backstop. Will look for more opportunities to encourage this.
I wonder if System76 has considered Raptor processors for their desktops. What is their roadmap towards more open hardware? Here goes my first recommendation to their customer support. I would consider a mini-desktop with Talos by System76 even though I'm primarily a laptop user.