The biggest slow down on MacOS compared to Linux is the default filesystem APFS (but hey HFS and HFS+ were also slow). But not just that, the Linux dirent cache is optimised to within an inch of its life (it's deliberately sized to match CPU cachelines among other optimisations). And one of the chunks of that slow down is upper / lower case checks (Mac filesystems be default treat upper and lower case as the same thing when it comes to matching a filename).
Because of that Linux works so much faster with small files, and text files are small compared to audio, video, etc.
