Approximately for raw game data, though a full ISO with CD audio tracks can exceed 500 MB . Platform
In the context of Sonic CD, the choice between NTSC and PAL is more than just region; it affects the game's core performance: Sonic liberado [NTSC][PAL][ISO]
A popular variant of "liberado" ISOs allows players to enjoy the Japanese/European soundtrack while playing the English-localized (NTSC-U) version of the game. Approximately for raw game data, though a full
The standard for North America and Japan. The game runs at full speed (60 frames per second). The game runs at full speed (60 frames per second)
The standard for Europe and Australia. Due to the slower refresh rate, PAL versions of Sonic CD originally ran approximately 17.5% slower than their NTSC counterparts.
Originally released in . The "Liberado" versions are community-patched "scene" releases.
For a modern experience without needing ISO patches, you might consider Sonic Origins or the Sonic CD Decompilation project, both of which offer widescreen support and selectable soundtracks by default.