I think it depends on what you’re saving and how you work with what you’ve saved.
My administrative archives live in DEVONthink and each broad area of responsibility gets its own database. (By “live in” I mean that I import them into DT.) Although I could store them in a hierarchy of Finder folders and use tools like Finder’s smart folders, Finder tags, Spotlight, Alfred/Raycast, or Claude Cowork to search for what I need, I find DT a nimbler and more cohesive workspace for big jobs—the kind where you need to retrieve a dozen documents of different types spanning a decade and probe the links between them for the better part of a day. DT makes it trivial to jump between viewing documents organized by folders to documents organized by tags to documents organized by type to documents organized by complex saved searches. You can archive email in DT in its native format, which means you can organize and search it with DT’s tools AND you can do email things with it too, like forward it to someone who needs to see it. I like having all the documents related to a particular matter—be they legal agreements, official documents, memos, notes, invoices, emails, whatever—ready to be configured for query and review however the task might warrant.
Simpler things that I might need access to for the short term don’t need anything more complicated than Finder folders on my desktop.
My research and learning material are stored in Finder folders in an Obsidian vault, which I also index in DT. I work with them in a very different way than I do the admin stuff, and Obsidian is better suited to that task. DT is a good place for document retrieval and review, but I don’t find it a congenial place for document creation and refinement—for that I prefer Obsidian.