Current org-mode user here, former Obsidian user. Although much more extensible than apps like Joplin, Notion or - god forbid - Evernote, Obsidian comes nowhere near the freedom you have in Org-mode. You can customize Obsidian to fit your workflow to some extent, but not by a whole lot. Then again: for most people that is enough. Most want to drive a car, not build it.
There is afaik no such thing as an org-agenda in Obsidian, which is a deal breaker for me. Also to do list handling is shoddy at best (it would probably be a perfect app if that got integrated, e.g. via a todo.txt format with a calendar) but alas.
If I weren't an org-mode user, Obsidian would probably be my pick. It is very nice in everything it does, but it just doesn't have that "edge" of creating a setup that is ugly, complicated an unrecognizable from its default. It may be ugly, but at least it's _your_ ugly.
That definitely gives you the basics. But it's worth noting that core org comes with a lot more functionality, e.g., calendaring, scheduling tasks (this is distinct from deadlines), blocking and ordered tasks, priorities, repeating tasks, timekeeping and time reporting. Some of this could be cobbled together in Obsidian by combining various plugins and some query code.
Obsidian vs. org-mode is pretty much like VScode vs. emacs. Obsidian has a more immediately accessible interface and a big community of plugins, but the available plugins tend to operate at a higher level of abstraction. Obsidian is also document-centric rather than outline-centric, although org-mode can be used either way. Calendaring isn't native in Obsidian and there is no org-agenda, but you can cobble together something similar with queries depending on your needs. Functionally, there's no real reason to switch from org-mode, but if you primarily want Roam-like features and find org-roam too confusing or awkward, you might consider it.
