For me it is less about the format and more about the ecosystem.
With no way to make a backup I'm reliant on them being always on and still around 10+ years later if and when I want to read it again.
But, the format also leaves much to be desired. The superbooks' "features" seem more like limitations. I cannot adjust text font or size, which is a feature! Something I've been able to do with every other ereader. I've also run into instances where the preview has text cut off even at 100% zoom. https://i.imgur.com/z8OldNU.png
With no way to make a backup I'm reliant on them being always on and still around 10+ years later if and when I want to read it again.
But, the format also leaves much to be desired. The superbooks' "features" seem more like limitations. I cannot adjust text font or size, which is a feature! Something I've been able to do with every other ereader. I've also run into instances where the preview has text cut off even at 100% zoom. https://i.imgur.com/z8OldNU.png