Joplin stores its files inside a database. Obsidian stores all notes as individual plaintext Markdown files.
In the first instance, that's clearly more future-proof and robust - your notes are immediately available in any application without a layer of abstraction. You can't have a single file corrupt and destroy all your notes.
I vastly prefer it for that reason. I want to know these notes are still going to work fine in 10 years, and be easily accessible.
But Trillium is not plain-text Markdown, so you're comparing apples to oranges. They're completely different approaches at their most base level.
Having been through the enshitification of Obsidian, it was important to me and many others to be not beholden to any vendor's file system. Trilium notes require Trilium to be instantly usable. My notes are useful and usable in Obsidian, Logseq, VSCode, and others, because they use plaintext Markdown files.