meau tender (the account formerly known as hector sperra)

I dunno anything about obsidian or notion or whatever, but joplin is pretty nice for taking notes.

not an obsidian user so i can't say anything about it, but i personally find apps like notion and ms word pretty frustrating because i'm not editing the text file directly. the notion block system doesn't feel intuitive to me.

i think a lot of programmers use vim/emacs/obsidian for their notes because they're already used to editing text and don't need to adjust to a new system

For me, the appeal of Obsidian vs Notion is mostly a data sovereignty thing - I'm not beholden to whatever whims the company has, especially wrt training LLMs on my data, everything exists permanently on my device and in an easily interoperable format. I don't have terribly complex needs of it, so I'm not the right person to really talk about "maintaining your second brain" or whatever, but the points in favour I'd bring up aside from "not continuing to store Data with Corporation" are:

• It has a pretty good extensions system that's per-workspace rather than global to the application, so you can have multiple vaults of notes with different purposes and use extensions to automate those purposes. This is both a blessing and a curse: things like themes are also per-vault, which is pretty annoying if you ever want to spin up a second vault for some other project, but realistically you can probably keep everything in one unless you end up with some conflicting automation desires.
• If synchronization between multiple devices is a must-have for you, their regular Sync offering does cost, and I haven't tried it for comparison here. If you already have a server that you can deploy a docker container on (or otherwise set up CouchDB) there's a self-hosted livesync extension that's a bit of trouble to get running, but seems to be rock-solid once you've got it set up, running entirely on your own infrastructure with E2E encryption. It supports both "live" editing where you can see edits as they happen between devices, or periodic synchronization or only on files being saved if you want to keep traffic down, and it has manual merging so you're not at the mercy of an automated merge if you happen to bring a device online with conflicting edits elsewhere. You can of course set it to merge automatically if it's super sure that's not a bad idea but if it's just you editing the notes and your devices are online most of the time, you'll never have to deal with it anyway. I've tested it for collaboration and it was pretty much fine so long as nobody edited the same paragraph together, but there's no live cursors or anything since it's not made for that.
• If you want to do some sort of analysis over your notes for whatever reason, the Dataview plugin lets you write and format queries directly in a note with their output embedded right there. I haven't played with this myself, but it's definitely cool. I'm not wholly convinced it isn't mostly just ricing for your zettelkasten, though. Your mileage may vary.
• One place it falls short is if you use Notion's databases a lot. It does have extensions that do this, but when I've used them, they haven't been all that great. I guess a directory of notes and Dataview to filter and display a table of information on them is probably, honestly, among the best solutions to this specific problem, but that's not a good thing - it's powerful, but a lot more effort and steps you out of visual editing.
• If you ever want to format your notes or some section of them using mdbook or a static site builder or whatever, they're always just going to be text files on your device. The only processing you're definitely going to need to do is converting Obsidian's wiki-style interlinking to actual markdown links to files, but that's trivial compared to authenticating with Notion's API and figuring out their block format. There are some other things, especially once you start dealing with extensions, but it'll always just be fairly simple text processing.
• Obsidian also recently added a new boards feature that lets you organize some short notes together on a 2d grid. It's pretty much freeform, but you can use it for a Trello board or similar, flowcharts, whatever - it's a pretty handy extra tool I don't think I've seen anywhere else (it reminds me a little of Scrivener?). The notes on a board don't have to be full notes, though they can link out. I haven't looked at the internal data structure of these for export purposes yet but I've been using one for a "desk" scratchpad of small thoughts I can more easily organize and spin off into larger notes, which works well for my scatterbrain. Like post-it notes that are inside my monitor instead of on it.

As for migration, apparently there's official support now. I can't attest to how well it works, I didn't have anything with Notion yet that I really needed to preserve.