You do realise that this is an article from eleven years ago?
And that this is a Mac magazine saying Mac is faster?
A number of users have run tests with very large vaults. When there’s a huge number of files, they noticed a slowing, but Obsidian was still usable.
Performance issues discussed recently have been around the speed of the graph and its impact, especially when it’s always kept live. But that’s been constantly tweaked so that it remains functional.
HDD will always be slower than SSD to load. Once loaded, it shouldn’t be an issue because plaintext is small and easily processed. Of course, if you add a huge number of images or videos your experience could be very different.