The manga is better because it has a more detailed storyline.
In the anime, there were many details that were overlooked. For example, Izumi’s night journey is mentioned in passing but never expanded on for the viewer to understand why she feels so resolved in her decision to have Akame kill her. There are also noticeable changes in the animation and character designs which detracts from enjoying it as an anime fan. Some may disagree with me and say these flaws concern minor issues or that they don’t change much of what happens but I feel like at least some parts should be consistent between formats to keep people engaged throughout the story line, even if their preferences differ somewhere else.
I hope this helps! Have a nice day 🙂