I currently have a System76 laptop, and sincerely regret my purchase. When I purchased it, the Framework was not out yet - I wanted to support a company that supports right-to-repair, and figured since they controlled the hardware, firmware, and software (Pop!_OS), it would be a good, stable experience. It has not been, and support has generally been poor. I know other people have had better experiences than I have, but personally, I won't be buying from them again.
I haven't personally used Purism, but former co-workers spoke really poorly of them. They were trying to buy a big batch for work, and said the build quality was awful. Additionally: https://youtu.be/wKegmu0V75s