As a former OneNote user who moved to Obsidian, I would say it's like comparing a go kart and luxury sedan. They both technically get you where you're going if you try hard enough. And if you're not going very far maybe all you need is a go kart.
My obsidian has turned into a personal Wikipedia and it's crazy how much it's improved my efficiency.
Never used Notion. I only toyed around with Evernote years ago and remember it being a cluttered mess. One Note worked alright for basic notes but I noticed I rarely referred back to them. With Obsidian, maybe it's because I put the time into my configuration but I have templates for different types of notes, a tagging system that works great for grouping and reference, and the internal linking really ties everything together.
My obsidian has turned into a personal Wikipedia and it's crazy how much it's improved my efficiency.