I don't know what it is, but I feel like the events of the anime and manga are in a slightly different order. The story feels like it's progressing a lot faster than the anime does. I think it's because we don't get a lot of Kagome in modern times at this point in the series, and in the anime it feels like every 5 episodes it becomes a Slice of Life school setting.

I am enjoying reading the manga. We get more of  InuYasha's inner thoughts and it's more clear where he stands with Kikyo in the manga. He has so much survivor's guilt. There's also some scenes in the manga that aren't in the anime that add more context to some events.