The R-rating certainly does give filmmakers some amount of freedom as they don’t really have to think about the rating when putting the story together.
We’ll see what we get when the new Hellboy makes its way to screens.
Nobody has to consider whether or not a scene will be too intense or violent for a PG-13 rating, an idea which can be difficult to judge as it is.
Considering that the new Hellboy is looking to be more of an action-horror movie, as opposed to the action-fantasy of the previous series, we’d expect that the movie is going to have its share of scary and violent moments, and doing that within the confines of a PG-13 story can be quite difficult to pull off well.