Well, the popularity of Guts and Count manga can be quite subjective. It often depends on factors like the storylines, art styles, and marketing. Sometimes, one might be more popular in one country or among a certain age group, but not necessarily everywhere or for everyone.
In the manga, Guts' character development is explored more deeply. The anime might focus more on visual action scenes. Also, the art style can vary, with the manga having a certain grittiness that the anime might not fully replicate.
Some people might find the Berserk Grunbeld novel difficult because of its potentially graphic content and the density of its world - building. But if you're used to reading dark fantasy or seinen manga - inspired novels, you may adapt to it more quickly and not find it overly hard.
The 'Guts' anime is a fairly close adaptation of the manga. It keeps the key elements intact, like character development and major plot points. However, there might be some added background details or minor character expansions to flesh out the story in the anime.