Anyone who's played Sonic CD probably knows that it has 2 completely different soundtracks. The original soundtrack is in the Japanese and European release. The North American version was delayed so a new soundtrack could be composed by Spencer Nilsen, who composed music for many Sega CD and early Saturn games. Why the NA version has a different soundtrack is beyond me.
Anywho, which do you think is better? Personally I love them both equally, but some zones like Collision Chaos have songs that fit the atmosphere better in the US version.