If what you have in your notion is mostly ideas, concepts, and thoughts, then Obsidian is a great choice. It is not as great for storing facts, because of the lack of something resembling Notion's robust database system.
So I use both: Obsidian for ideas, beliefs, concepts, explanations, class notes, etc. Notion for Goals, freelance client project info, job hunt tracking, to watch/read lists, images and links for internet arguments, plans for video games, travel plans, technical solutions, exercise and practice routines.
I do like Notion. I have been a paying customer for the last year. But I find that it has too many limitations for how I work. Why can I not customize colors? Why is there no plain text block? Why is there not a simple table? So many basic things seem missing.
1. It is easy to back up or export my data
2. Great UI! May be its just me, I care about the UI a lot and if it is nice, I seem to be writing more
3. Support for templates, so that I can write daily journal/entries with predefined fields
4. Support for keyboard shortcuts (or mouse-less operations) so that I can link or embed documents quickly