Because the file is smaller and indexed, the Dreamcast’s processor (or an emulator) can seek data points more efficiently than it can with a fragmented GDI folder. How to Get or Create a Sturmwind CHD
It reduces file size without losing any data.
Most Dreamcast ODEs and emulators (like Flycast or Redream) read CHDs faster than uncompressed formats. Why Use CHD for Sturmwind?