For people planning on reading, the only thing is a pretty big trigger warning for rape. Things like the extreme gore and torture are to be expected, but it's done in a fun way.
I felt the manga focused way more on characters like Ichi and Kaneko, but it didn't add all that depth to them whatsoever. I think Kakihara was definitely more pushed aside in the manga, while the movie put a fair amount of time for each character recurring the story.
Absolutely loved the art though, some panels were incredible because of the special effects and the facial expression of the characters. Overall, pretty good and fun to read.