In my experience it comes down to the type of book. Novels and narratives with just a few supporting tables, illustrations, or diagrams? EPUB is probably prefer

In my experience it comes down to the type of book. Novels and narratives with just a few supporting tables, illustrations, or diagrams? EPUB is probably preferable. But anything remotely technical with code snippets, diagrams, screenshots, tables, etc, PDF is going to be infinitely better.