truth be told; i don't prefer either cbz or epub over pdf as the image files included in light novels and other media are ofter scaled down in an odd method that adds a border to the image. no amount of adjusting scaling settings will ever fix seval of them from the eye sore the format makes them to be.
I'm only using such formats as in recent years, several books seem to be found only in such formats. its annoying, I'd rather an pdf or actual image files any day.
the only other recent trend I've seen worst is light novels' illistrations aren't kept proper place that they fit with-in the context of reading, like edting it to place duplicates only at the begining of the book and then removing the original from their intented place with in the novel.
Or even worst the light novels' found online that have their illistrations removed.