Website: https://obsidian.md/
There is one major difference in the way notes are linked. Roam is essentially an outliner: every bullet-point has a unique ID and you can't link directly to it. That way you can
- reference specific blocks of texts (Obsidian only allows to link to headings)
- display the entire block in the backlinks section (Obsidian only renders a set number of words around that mention)
This is a useful feature. You can write a lot of one-liners in your daily notes, and then refer to each of them from other notes, as demosntrated here